Cellular Phones in Class 1, Division 2/Zone 2 Hazardous Locations

Copyright Material IEEEPaper No. PCIC-2006-4

Allan Bozek P.Eng, MBAMember IEEEEngWorks Inc.Calgary, Canadaabozek@engworks.ca

Ken MartinMember IEEEBrodwell Industrial Sales Ltd.Calgary, Canadakmartin@brodwell.com

Marty ColeSenior Member IEEEHubbell CanadaToronto, Canadamcole@hubbell-canada.com

Abstract - The risk associated with using a portablecellular phone in a Class I, Division 2 or Zone 2 hazardouslocation is evaluated. Experimental trials were performedon a representative sample of commercial grade cellularphones using the guidelines provided in ISA-RP12.12.03-2002 "Recommended Practice for Portable ElectronicProducts Suitable for Use in Class I and II, Division 2,Class I Zone 2 and Class l/l, Division I and 2 Hazardous(Classified) Locations" [1]. The ignition risks aresubsequently classified according to a framework rankingsystem for ignition sources developed by Rew and Spenser(1997)[2]. The results are used to construct a probabilitymodel that estimates the risk of a cell phone igniting aflammable atmosphere in a Class I, Division 2 or Class I,Zone 2 hazardous location.

All cell phones evaluated did not meet the ISA-RP12.12.03-2002 requirements for a PEP 2 (PortableElectronic Product) device and therefore could not beconsidered "incapable of causing an ignition under normaloperating conditions" as per the PEP definition. Additionaltesting and analysis of the high risk cell phone componentsindicated a very low probability of ignition even under idealconditions. A Monte Carlo simulation of the probabilitymodel estimated the odds of a cell phone causing a fire orexplosion in a Class I, Division 2 or Class Zone 2hazardous location as being 1 .16E-06; or one in a million.

Index Terms - Cellular mobile cell phones, Hazardouslocations, Ignition probability model.

I. INTRODUCTION

In recent years, the cell phone has become the mostwidely used technology media for voice communications.In North America alone, there are estimated to be 180million mobile phones in use; with on average 1 mobilephone for every two persons. Their convenience andportability make it an ideal means of communication withina petrochemical facility. This convenience must beweighed against the risk of a fire or explosion inadvertentlycaused by the use of a cell phone within a hazardouslocation.

The purpose of this paper is to estimate the riskassociated with using a standard commercial grade cellularphone in a Class I, Division 2 or Class I, Zone 2 hazardouslocation. Class I, Division 2 and Zone 2 locations wereselected as the basis for the study since 95% of allhazardous locations within North America are assigned this

classification. It should be cautioned that the risk of usingcommercial grade cell phones in a Class I, Division 1 orClass I, Zone 1 hazardous location is an order ofmagnitude higher and is not addressed within the scope ofthis paper.

Results from previous research studies are examinedand the current industry regulations related to cell phoneuse in hazardous locations is reviewed. An industrial usersurvey is conducted to determine the extent of cell phoneuse by petrochemical operations and how their use ismonitored in hazardous locations.

To estimate the probability of a cell phone igniting aflammable atmosphere, a series of tests are performed ona sample cross section of cellular phones. The results aresummarized and incorporated into a probability model thatapproximates the risk of a cell phone igniting a flammablemixture within a Class Division 2/Zone 2 hazardouslocation.

II. OVERVIEW OF CELL PHONE TECHNOLOGY

A cell phone is essentially a radio transmitter/receiveroperating in the 800 Mhz and 1900 Mhz frequencyspectrum. A cell phone communicates to a network ofbase stations which in turn are linked to the telephonenetwork.

Cell phone technology has evolved over a number ofproduct generations to where it is today. In 1981, the 1stgeneration mobile phone began operation with theintroduction of analog cellular service called AMPS(Advanced Mobile Phone Service). The 1G cell technologyallowed users to place calls and converse seamlessly asthey moved from cell to cell locations. A typical 1Ghandheld mobile phone was large, heavy and expensiveand required 6 watts of power to transmit and receive.

The 1G was rendered obsolete in the early 1990's withthe introduction of the 2nd generation based on digitalcellular technology. Digital cellular technology increasedthe number of simultaneous phone conversations for thesame range of radio spectrum and allowed for servicesbeyond simple voice communications. As cellular phonesincorporated additional features such as personal digitalassistants, text messaging, cameras, internet browsers andemail capability, a 2.5G generation of mobile phonetechnology emerged. The majority of mobile phones in usetoday are 2.5G.A 3rd and 4th generation of cellular phone technology is

currently in development. As with all microprocessor

1-4244-0559-9/06/$20.00 ©2006 IEEE

technologies, each generation reduces the size, weight,cost and power consumption while improving the features,reliability and the ease of manufacture.

Fig. 1 provides a simplified block diagram of a 2.5Gmobile phone.

iDigpa

Sa§6band wMbrato

kra

aIAhlNBog RF 1M,bbphone Rbaseband =|r andver

Chp_ | ~~~~~~~~~~AUDC Adg|| | rcher atteql

IMahagemen Chargitlng d

Fig. 1 Mobile Phone Block Diagram

IlIl. SUMMARY OF PREVIOUS RESEARCH STUDIES

The majority of documented cases where a cell phonewas identified as a potential ignition source are in retailgasoline operations. Within the petroleum and chemicalindustry, only one incident was identified where a cellphone was considered a potential source of ignition. Themajority of research to date has focused exclusively onretail gasoline operations.

Self-service gasoline pumping operations requires thepublic (unknowingly or otherwise) to perform activitieswithin a Class 1, Division 2/Zone 2 hazardous location. Inseveral cases where a gasoline fire resulted during fillingoperations, a cellular phone was identified as possiblesource of ignition. Widespread media coverage led to thegrowth of an urban legend where cell phones were quotedas being the primary source of ignition in these events.

In response to public awareness, several retail gasoperators issued directives to their staff to post warningsigns and monitor the use of cell phones near fueldispensers. If a customer was observed to be using a cellphone while pumping fuel, the operator was to cease fillingoperations. Mobile phone manufacturers also respondedby incorporating warnings in their user manuals asillustrated in Fig. 2.

Following the accident investigations, a number offormal studies were commissioned to objectively assessthe danger of using a cellular phone during fillingoperations. All studies concluded that it was highly unlikelythat a cell phone was the primary source of ignition andthat static electricity as the most probable cause. Severalformal statements were issued as follows:

The University of Oklahoma Center for the Study ofWireless Electromagnetic Compatibility study (August

2001); Investigation of the Potential for WirelessPhones to Cause Explosions at Gas Stations,concluded that '...research into the cell phone - gasstation issue provided virtually no evidence to suggestthat cell phones pose a hazard at gas stations....While it may be theoretically possible for a sparkfrom a cell phone battery to ignite gas vapor undervery precise conditions, the historical evidence doesnot support the need for further research. '13]

Exponent Failure Analysis Associates, Menlo Park,California (December, 1999) study, Cell Phone Usageat Gasoline Stations, concluded that "...the use of acell phone at a gasoline filling station under normaloperating conditions presents a negligible hazard andthat the likelihood of such an accident under anyconditions is very remote." The report also noted"automobiles (which have numerous potential ignitionsources) pose a greater hazard... Finally, otherpotential ignition sources are present, such as staticdischarge between a person and vehicle." [4]

The Institute of Petroleum hosted a technical seminarentitled "Can mobile phone communications ignitepetroleum vapour?" (March 2003) issued a pressannouncement stating "The seminar showed thefindings of research undertaken to date demonstratingthat although the majority of mobile phones are notspecifically designed and constructed to prevent themigniting a flammable atmosphere (in accordance withstandards for 'protected equipment) the risk theypresent as a source of ignition is negligible." [5]

Fig. 2 Excerpt from a Mobile Phone Users Manual

In contrast to the large number of filling station fireswhere a cell phone was listed as a possible ignition source,only one industrial incident was noted. The incidentinvolved a flash fire on an offshore platform in the Gulf ofMexico. A contract panel specialist was working on anopen panel that used fuel gas for instrumentation. Thecontractor's cell phone rang and was activated by flipping itopen. A flash fire occurred and the contractor receivedsecond degree burns to his forearms and face. Theincident prompted the US Department of the Interior toissue Safety Alert No. 5 in March of 2002 cautioning theuse of portable electronic devices in hazardous locations.The bulletin recommended the use of hot work permits,

Potenitially Explosive Atmnosphei es

Tuna of votir radio priodtct prior to eiie ing any area with a potentiallvexplosive atinoplere, unless it iS a radio product type especiallv qualifiedfbr ise in silch areas as Intrniisically Safe" (fbr example. Factory Mutial,(SA. or UL approved) Do niot remove, iistall, 01 charge batteries in suchareas. Spaiks in a potentially explosive atinospliehe caLi caiise ali explosionor fire resulting in bodily iJuiry or ex eni deathli

NOTE: Tile aieas wvith potentially explosive atnospheres referred toabove include fueling areas suci as below decks on boats, fuel orcliemical transfer oi storage facilities arleas Wvhere the aircontains chemicals or particles, such as grain, dust or metalpowders. and anv othei aresa heere you wou1d normally beadvised to turn off vour vehicle engine. Areas w-ith potentiallvexplosive atmnospheres are often but not alwvays posted.

intrinsically safe devices or third party approved devices inhazardous locations [6].

The US Department of Interior Mineral ManagementService (MMS) Division followed up with a formalinvestigation. The cellular phone involved in the incidentwas sent to a third party testing agency for a battery oftests in a controlled laboratory environment. On conclusionof the investigation, the Department of Interior issued thefollowing statement:

"Based on this information and MMS's investigation, wewere unable to conclusively identify the ignition sourceof the fire. However, we have not ruled out thepossibility that the fire could have been ignited by staticelectricity, a spark from the metal master control paneldoor coming into contact with a metal handrail, or awrench striking metal inside the control panel. '17]

Although the investigation concluded that it was highlyunlikely that the cell phone was the primary source ofignition, the advisory cautioning against the use of cellularphones in hazardous locations remained in place.

IV. INDUSTRY REGULATIONS AND PRACTICES

A. Government Regulations

Government regulations related to cell phone use inhazardous locations vary in scope and detail. In the US,the NEC does not make a direct reference to the use ofcellular phones but implies they fall under the generalclassification of electrical and electronic equipment. NECArticle 500.8 [8] requires that all electrical and electronicequipment be approved for use in hazardous locations andshall be identified by any of the following:

1)2)

3)

Equipment listing or labelingEvidence of equipment evaluation from a qualifiedlaboratory or testing agencyEvidence acceptable to the authority havingjurisdiction such as a manufacturer's self evaluationor an owner's engineeringjudgment.

In Canada, the Canadian Electrical Code requires thatall electrical equipment used in hazardous locations besubject to the rules of section 18. A note in the CECappendix specifically addresses battery poweredequipment including "transceivers, paging receivers andbattery or voice powered telephones" and requires suchdevices be approved by a third party certification authorityfor use in a hazardous location [9].

The CEC requirements are further reinforced by asuggested change to the 2005 Occupational Health andSafety Regulations that specifically requires cellulartelephones used in hazardous locations be certified.

In Europe, ATEX 94/9/EC directive requires allequipment used in potentially explosive atmospheres becertified for the appropriate gas group, temperatureclassification and be suitably labeled [10].

B. Recommended Practices

From a regulatory perspective, it would appear thatcellular phones, unless certified for use, shall not be usedin a Class hazardous location. This clarity was somewhatcontradicted by the ISA publication ISA-RP12.12.03-2002"Recommended Practice for Portable Electronic ProductsSuitable for Use in Class I and II, Division 2, Class I Zone 2and Class Ill, Division I and 2 Hazardous (Classified)Locations"

ISA-RP12.12.03-2002 was written as a guideline for thesafe use of general purpose battery powered portableequipment in hazardous locations. It was developed toaddress situations where portable and battery poweredequipment was required, but unavailable as listed for use ina classified location. This may be due to rapidly changingtechnology, or the need for time consuming and expensivethird party certifications for products with a limited market.

ISA-RP12.12.03-2002 describes the minimumprecautions required for using a portable electronic devicein a classified location. In Class 1 Division 2/Zone 2locations, a product may be listed, or used with a gas freework permit, or when the product meets the design andperformance criteria for a PEP (Portable ElectronicProduct) as specified in the document.A PEP product is defined as a "battery powered or

photovoltaic cell powered apparatus that can be hand-heldor that is intended for use while worn on a person's body."Certain PEPs may be suitable for use in hazardouslocations if they are deemed "incapable of causing anignition under normal conditions."

PEPs are further broken down into PEP 1 and PEP 2product categories. A PEP 1 device does not requirelabeling or permitting for use in a hazardous location. Incontrast, a PEP 2 device requires a PEP 2 marking statingthe evaluating company name and the supportingdocument reference number or code.

Examples of PEP 1 products include electronic wristwatches and hearing aids. Examples of PEP 2 devicesinclude calculators, hand held testers and "some cellphones".

C. Industry Practice

To determine the extent of cell phone use in hazardouslocations, an on-line survey was conducted. The surveytargeted firms in the oil and gas industry who wereoperators of large scale petrochemical facilities. Results ofthe survey indicated that cell phones are in general use byOperations personnel, however, they are not the primarymeans of communication in classified areas. Allcompanies responding restricted the use of cell phones inhazardous locations with 60% banning them outright.Where cell phones were permitted, they were required tobe listed and approved by a third party certificationauthority. Appendix A summarizes the results of thesurvey.

V. REQUIREMENTS FOR IGNITION OF AFLAMMABLE ATMOSPHERE

To further examine this issue, a basic understanding ofthe ignition process is required.

To ignite a flammable atmosphere:a) An ideal flammable mixture must be present in

sufficient quantity to create a hazardb) An active ignition source must be presentc) The ignition source must have sufficient energy

to ignite the flammable atmosphere

A. Requirements for an Ideal Flammable Gas Mixture

For an ideal flammable mixture to exist, the flammablematerial must be in the vapor or gaseous state; the vaporto air mixture concentration must be between the lowerflammable limit (LFL) and the upper flammable limit (UFL)and the temperature must be below the auto-ignitiontemperature of the flammable material. The flammableregion, as illustrated in Fig. 3 is the area where thepresence of an external ignition source may potentiallycause a fire or explosion.

FLASH INT

Fig. 3 Flammability Relationships

The probability of an ideal flammable gas vapor-airmixture being present at any given time is influenced by anumber of material and environmental factors. Theflashpoint of the flammable material, the material's densityrelative to air, the source, rate and geometry of release andthe quantity of air movement all influence the degree andthe extent of the hazard. To assess if a hazard exists atany given time requires quantifying these variables. This isoften very difficult to do in practice.

The purpose of a hazardous area classification is tosubjectively assess the probability of a flammable mixturebeing present within an area at any given time. Facilitieswithin North America may be classified using the Divisionor Zone method of area classification. Class I, Division 1locations are areas where there is likely to be ignitableconcentrations of flammable gases or vapors. Class I,

Division 2 areas are locations where ignitableconcentrations of hazardous materials are unlikely to exist;and should they exist will do so for a very short time.

The Zone method of area classification divideshazardous locations into three risk categories. A Class I,

Zone 0 location is where a flammable concentration of a

gas or vapor is expected to exist on a continuous basis.Class I, Zone 1 areas are locations where a flammableatmosphere is likely to exist; and a Class I, Zone 2 locationis where a flammable atmosphere is unlikely to exist. Itshould be noted that these subjective probabilities arebased on normal operating conditions. Catastrophic failureevents are not considered.

API RP 505 provides additional guidance in defining ahazardous area classification based on the theoreticalpresence of a hazardous mixture as illustrated in Table I.

TABLERelationship between Zone Classification and thePresence of Flammable Mixtures (API RP 505) [11]

Zone Flammable Mixture Present % of time peryear

0 1000 hrs or more per year > 10%

1 > 10hrs and < 1000hrs peryear 0.1% - 10%

2 > 1 hr and < 10 hrs per year 0.01% - 0.1%

Unclassified < 1 hr per year < 0.01%

B. Requirements for an Active Ignition Source

For a device in intermittent use, the probability of thedevice becoming an ignition source in the presence of aflammable gas is a function of how often and for whatduration the device is used. A cell phone can beconsidered an intermittent use device and is deemed'active" when it is in the process of transmitting andreceiving radio frequencies.

To conserve power, a cell phone will operate in a "sleep"mode awaiting an incoming signal or activation by theUser. While the cell phone is in sleep mode, power levelsare reduced to a minimum and the risk of ignition isnegligible. Once the cell phone receives an incoming callor is activated by the User, it may be exposed to aflammable atmosphere and has the potential to become anignition source.

C. Ignition Source Energy Requirements

For an electrical ignition to occur an electric spark mustarc across a contact gap that exceeds the minimumquench gap distance and the spark energy generated mustexceed the minimum ignition energy requirements for theflammable material. Quenching refers to the "cooling"process that occurs when the heat energy of a spark orflame is transferred to an adjacent surface. The quenchgap is the largest passage that can prevent propagation ofa flame through a passage when it is filled with aflammable fuel-air mixture.

The size of a quench gap is experimentally determinedand varies with the mixture composition, the surfacegeometry and the pressure and temperature of thesurrounding atmosphere. A 2.0 mm quench gap distanceis typically used for methane and 0.6 mm gap used forhydrogen.

The minimum ignition energy required to ignite aflammable mixture varies with the material composition andthe air mixture ratio. Fig. 4 illustrates the minimum sparkenergy required to ignite methane and hydrogen as afunction of % volume to air concentration. The ignitionspark energy is at a minimum at the stoichiometric airmixture ratio. The energy required for ignition increases asthe percent air/mixture ratio deviates from thestoichiometric ratio. Table II illustrates the materialcharacteristics; minimum ignition energy and minimumquench gap distance required for the ignition of methaneand hydrogen.

CH4Ar H.

2A10 -

E 1.0 -

I..........

0

StoichlorretricCH4 Air Mixture

0.274 mJ

AWrHFM ixture0-01'7 mJ

I I I I

20 40 60 80Fuel (% Volume)

Fig. 4 Spark Energy Required to Ignite Methane andHydrogen

TABLE II

Physical Properties of Hydrogen and Methane

Autoignition temperature 5200 C 6300 CLower flammable limit 4% by vol. 5.3% by vol.Upper flammable limit 75% by vol. 17% by vol.Stoichiometric mixture 29.5% by vol. 9.5% by vol.Density relative to air at STP 0.07 0.55Minimum ignition energy 0.017 mJ 0.274 mJGroup Classification Group B, IIC Group D, IIAQuench Gap Distance 0.66 mm 2 mmMinimum ignition energy 0.017 mJ 0.274 mJ

VI. CLASSIFICATION OF IGNITION SOURCES

A number of statistical models have been developed forthe purpose of classifying ignition sources. The frameworkdeveloped by Rew & Spencer (1997) builds on the

research done by a number of previous referencesincluding Cox, Lees and Ang [15]. The model provides ameans of ranking ignition sources into various groupsbased on their ignition potential as illustrated in Table Ill.Ignition sources range from open flames that are assignedan ignition probability of 1.0 to intrinsically safe deviceswith an ignition probability of 0.0.

For reference purposes, a typical zone 2 approvedequipment device would fall into the "weak" category withan ignition probability of 0.01 [15].

TABLE IlIlFramework Ranking System for Ignition Sources

Rew & Spencer (1997) [2]

Category Examples of Ignition Ignition(Strength Sources Potentialof Source)

Pilot LightsCertain Fired Heaters p = 1

Flares

Strong Hot WorkP > 0.5Electrical Faults, Smoking>0.

Vehicles, Substations,

Medium Unclassified electrical 0.5 > p > 0.05Medium equipment, Engines, Hot 0.>p .5surfacesOffice Equipment, Electrical

Weak Appliances p<00Mechanical Sparks p <0.05Static electricity

Negligible Intrinsically safe equipment p = 0Radio Frequency Sources

VII. EVALUATION OF A CELL PHONE AS ANIGNITION SOURCE

To evaluate and classify the ignition potential of a cellphone, the design criteria and test methods outlined in ISA-RP12.13.03-2002 for a PEP 2 device is used as a basis.

The PEP2 criterion applicable to a cell phone is asfollows:

1) Radio frequency transmission energy is limited toa safe level

2) No sparks visible in normal operation3) No power on-off switch that directly interrupts the

battery current4) No motors unless it can be demonstrated that the

motor incorporates non-arcing technology5) No external connections of accessories are used

in the hazardous area6) Exposed terminals (battery charging terminals)

are recessed or diode protected to prevent adischarge caused by the accidental shorting of theterminals

7) No excessive temperatures in normal operation8) Cell or battery is secured so it will not fall out in a

specified drop test9) No damage that exposes electrical/electronic

circuitry as a result of the drop test

Hydrogen Methane

The ISA performance tests were applied to arepresentative sample of 8 cell phones from five differentmanufacturers. Upon completion, each cell phone wasdismantled and examined for any components that mightpose an ignition risk. Where a potential ignition hazardwas identified, additional tests were done to further assessthe ignition hazard.

Appendix B provides a complete summary of the testresults. The following sections discuss the PEP 2 criterionand provide comment on the ignition risks identified.

A. Radio Frequency Energy

Radio devices that emit electromagnetic frequenciesmay create a spark hazard in the presence of an opencircuit antenna loop as illustrated in Fig. 6. The extent ofthe hazard is related to the strength of the radio frequencyradiation emitted while transmitting.

Base Station

EleQtwmagneticeF re'uency

Mobile Phone

Fig. 6 Induced Spark Hazard from RF Radiation

B. Arcing/Sparking Components in Normal Operation

1) Contacts and Switching Devices: The potentialfor a cell phone to arc or spark in normal operations isrelated to the technology and energy switching levels usedfor keyboard and switching functions. All cell phonesexamined used a dome switch keyboard technology. Thedome switch technology uses a hybrid of membrane andmechanical components to allow two circuit board traces tocontact under a plastic "dome" or bubble.

One key advantage of the dome switch keyboardtechnology is that it effectively seals the switching contactsfrom the environment. While primarily designed to preventliquid contamination of the keyboard, it also creates avapor-tight barrier that effectively eliminates the keyboardas a potential source of ignition.

ISA-RP12.12.03-2002 requires only the on-off switch beexamined for arcing-sparking potential. All cell phones inthe test group used the same switch for on-off functionsindicating an electronic circuit switch was used for powercontrol. A dome membrane type switch was observed inall cases. On this basis, the ignition risk associated withswitching and control functions was deemed negligible.

2) Vibrator mechanism: Seven of the eight cellphones in the test group incorporated a vibrate ring feature.The vibrator mechanism on a typical mobile phone consistsof a DC micro-motor turning a counterweight. The spinningcounterweight provides the vibration effect.

The micro-motor used for a cell phone vibratormechanism incorporates a coreless motor design. Acoreless motor replaces a rotating iron armature with a lightweight copper coil. The copper coil then rotates around astationary magnet system. Fig. 7 illustrates a corelessmicro-motor design.A typical vibrator pager micro-motor will have a voltage

input of 1.25V and a running current of 120ma. Within thecellular phone circuitry, the vibrator motor is controlled by amicro motor driver chip that controls and protects the motoroperation. The controller chip will provide a stabilized DCoutput and limits both the temperature and current to themotor.

The safe radio frequency energy transmission levels aredefined in BS 6656 "Assessment of inadvertent ignition offlammable atmospheres by radio-frequency radiation -Guide" [12] and are used as a PEP performance criterion.The maximum RF energy that may be emitted from a PEP2 device must be less than:

* 2 W maximum output averaged over 20microseconds for Groups A and B and Group IIC

* 3.5 W maximum output averaged over 100microseconds for Group C and Group IIB

* 6 W maximum output averaged over 100microseconds for Group D and Group IIA

Under normal operating conditions, a 2.5G mobilephone radiates between several hundred milliwatts and 0.7watts of RF energy depending on the signal strength to thebase station (the weaker the signal the more power amobile phone handset will send). This is well under themaximum 2 watts of radio frequency energy consideredsafe under all conditions and therefore eliminates RFenergy as a potential ignition source.

BrUsh Commutator,Permanent Magnet

CounterweightX

Wire Leads

Cor es:s Rotor

Fig. 7 Coreless Vibrator Micro-motor

The coreless micro-motor design requires a preciousmetal or graphite brush commutator system. Acommutator system is an arcing sparking component bynature and must be considered a potential ignition source.To determine if the vibrator function might pose an ignitionrisk, micro-motors were removed from 5 of the 7 cellphones in the test group and placed in an explosionchamber with a Group IIC stoichiometric hydrogen mixture

to simulate a worst case flammable mixture environment.The micro-motors were alternately energized for 10seconds with a 1.5V DC power source to simulate avibrator operation.

No ignition events were observed with any of the micro-motors tested. Based on these results, the probability ofa cell phone micro-motor igniting a flammable atmospherecan be considered negligible.

C. Drop Tests

ISA-RP12.12.03-2002 requires a PEP2 certified productto be dropped from a height of 2 meters to a horizontalconcrete surface. The device must survive withoutexposing any internal circuitry or the battery becomingdisconnected. The test is repeated six times in a variety oforientations.

Within the test group, only one cell phone survivedwithout the battery disconnecting on impact. In all othercases, the battery separated from the cell phone one ormore times. In all cases, when the battery wasreconnected, the cell phone worked properly with nophysical or operational damage observed.

The probability of a spark being created as a result ofthe battery disconnect is difficult to assess. The more likelyscenario would be the dropped object itself posing theignition risk. In theory, an object the size of cell phone candischarge 10-20 mJ of energy under ideal conditions. Thisrisk is common to all objects. Without conclusive resultsand given the remote likelihood of a battery disconnect ordropped object creating a spark hazard, the spark ignitionpotential of a dropped cell phone was given a weak ratingin accordance with the Rew and Spencer (1997) model.

D. Battery circuit

Most modern cell phones use a Lithium Ion battery cellas a power source. The Li-Ion technology provides a lowenergy-to-weight ratio; do not suffer from a memory effectand have a very low self-discharge rate when not in use.There are however, some inherent risks associated with Li-Ion battery cells. An unprotected Li-Ion cell can easilyrupture, ignite or explode if short circuited, over charged orexposed to high temperatures.

To minimize the risks associated with using Li-Ion celltechnology, a built-in IC protection circuit is incorporatedinto the battery pack as illustrated in Fig. 8. The batterycell also incorporates a cell vent system designed to limitthe internal pressure to a safe level should a fault occur.

There have been a number of recent incidents where aLi-Ion cell has exploded causing personal harm in the formof 2nd degree burns. The mobile phone industryresponded by launching a large scale recall of the mobilephones involved. What was later discovered is that manyof the battery units at fault were counterfeit cellsmanufactured by unauthorized third parties. The batterycells did not incorporate the battery protection circuits thatall legitimate manufacturers use in their design.

To insure public safety and to promote standardizationof Li-Ion cell protection systems, the IEEE is currently inthe process of releasing IEEE P1725 "Standard forRechargeable Batteries for Cellular Telephones" [13]. The

standard provides specific recommendations designed tolimit component failures that lead to hazards. The standardrecommends the use of output current limiting devices,thermal protection circuits and at least two overchargeprotection functions designed to prevent overcharging abattery cell. The standard also provides recommendationson connector/terminal arrangements designed to preventaccidental short circuits.

All cell phone manufacturers in the test groupincorporated a battery protection circuit to prevent shortcircuits and with the exception of one cell phone, allincorporated recessed terminals. It should also be notedthat despite the protection circuitry, all batteries werelabeled with warnings that burns or injury could result fromshorting the battery terminals with metal objects.

To determine the effectiveness of the protectioncircuitry, the battery terminals were shorted in a darkenedenvironment to determine if any visible sparks could bedetected. No sparks were observed throughout the testgroup. The test results were consistent with a similar studydone in 1999 by the Center for the Study of WirelessElectromagnetic Compatibility, University of Oklahoma [3]on 3.6V Li-Ion cells. Based on these observed results, theignition potential associated with shorting the batteryterminals was considered negligible.

Fig. 8 Lithium-Ion Battery Protection Circuit

E. Excessive Temperatures in Normal Operation

In normal operation, the operating temperatures of cellphone components are well below the auto-ignitiontemperatures of all flammable materials.

Under abnormal conditions, the only component thatcould potentially act as a heat source is a short circuitedbattery. To determine if this was a potential risk, a test wasperformed to measure temperature rise under short circuitconditions. The surface temperature of the battery cell wasmeasured prior to the battery terminals being shorted for aperiod of ten minutes. The temperature was againmeasured and compared to the original reading. In allcases, no measurable increase in temperature was noted.This implies that probability of a surface temperature

reaching a flammable material autoignition temperatureeven under abnormal operating conditions is remote. Theignition risk associated with excessive temperatures wasconsidered negligible.

F. Static Electricity

Although ISA RP12.12.03 does not specifically addressthe potential for static build-up on PEP, it is worthdiscussing as many of the incidents involving cell phones ina fire or explosion were eventually traced back to a staticdischarge.

For a static ignition to occur, a capacitive build-up ofenergy must occur on a non conductive surface. Theenergy stored on the charged surface must exceed theminimum ignition energy of the fuel mixture. The storedenergy E on a part of capacitance C at a voltage V isbased on the following relationship:

E = 0.5CV2

G. Test Results Summary

None of the cell phones tested met the ISA RP12.13.03-2002 criteria for a PEP 2 device. The primary ignition risksnoted were related to the risk of the battery separating fromcell phone circuit or an impact spark discharge after beingdropped. All other ignition risks were deemed negligible.Given the potential for a battery disconnect or spark impactdischarge, the overall ignition source ranking for a cellphone best be described as a "weak" with an ignitionpotential of between 0.0 and 0.5 in accordance with theRew and Spenser (1997) framework.

VIl. COMPUTER MODELLING

As discussed in section V, the ignition of a flammablemixture requires an ideal flammable mixture and an activeignition source with sufficient energy to ignite the mixture.The relationship can be described in mathematical termsas follows:

The breakdown strength of air is around 6MV/m,therefore the minimum quench gap distance of 2mmcorresponding to methane requires an ignition voltage ofapproximately 6kV. A stoichiometric mixture of methanerequires 0.274 mJ of energy for ignition and thus requiresan object to have a capacitance of at least 11 pF. Similarly,a stoichiometric mixture of hydrogen requires 0.017 mJ ofenergy and therefore requires the object to have acapacitance of 0.94pF. Smaller objects require a highervoltage to provide the required ignition energy.

To determine if an object the size of a cell phone canbuild up a sufficient capacitance charge, the guidelines forenclosures provided in ANSI/ISA 12.00.01-2002 (IEC60079-0 Mod) "Electrical Apparatus for Use in Class 1,Zone 0,1&2 Hazardous (Classified) Locations: GeneralRequirements" [14] was used as a test criteria for cellphone enclosures.

By limiting the surface area of a plastic enclosure to lessthan 100 cm2 for Group IIA (methane), and 20 cm2 forGroup IIC (hydrogen) an object can be consideredinherently safe. The surface area dimensions for all cellphones in the test group ranged between 180 and 225 cm2.Although the surface area exceeds the minimum no-testcriteria, the surface area is minimal when compared to thesurface area of a human body.

The male human body has a surface area ofapproximately 18,000 cm2 and a capacitance in the rangeof 100-300 pF under ideal conditions. A human bodycharged to 6 kV stores around 3.6 mJ of energy; more thanenough to ignite a hazardous mixture under idealconditions. The ratio of charge build up by a cell phonecompared to a human body is insignificant under thesecircumstances. In all likelihood, a static charge build-upwould be the result of a human body static discharge ratherthan a static discharge from the cell phone itself.

It should be noted that a metallic object such a mobilephone case can act as an electrode and increase the riskof a static electric discharge from a charged human body.

Based on the analysis, the ignition risk resulting from astatic build-up on the surface area of a cell phone wasconsidered negligible.

where:p(FE)t = p(FA) x p(IGN) x Ta/(Ta+Ti)

p(FE)t = Probability of a Fire or Explosive Event at time tp(FA) = Probability of a flammable gas is presentp(IGN) = Probability a spark ignition event of sufficientenergyTa = Time a device is activeTi = Time a device is inactive

All variables in the equation are subject to a range ofprobabilities which lends itself to a Monte Carlo statisticalsimulation analysis. A Monte Carlo simulation was appliedto a range of different values for p(FA), p(IGN), Ta and Tito generate a theoretical range of values for p(FE)t. Thesimulation was run for 500 iterations using the followinginput models.

A. p(FA) - Flammable Atmosphere Present

The probability of a flammable mixture being presentwithin a Division/Zone 2 classified location at any giventime was modeled as a uniform distribution as illustrated inFig. 9. The distribution approximates the probability of aflammable gas being present of between 1 hour and 10hours per year which is consistent with definition of Class I,Division 2 or Class I, Zone 2 hazardous location.

0-5

0-10 h iurs per year 1oTh

Fig. 9 Probability Distribution for a Flammable Gas beingPresent within a Class Division/Zone 2 Area

B. p(IGN) - Spark Ignition Event of Sufficient Energy

To model the probability of ignition risk, a triangulardistribution was selected with a range of values between0.01 and 0.05 with a mode (most likely) value of 0.02. Theprobability distribution is illustrated in Fig. 10.

The value 0.01 was selected as the lower bound basedon premise that a certified Class I, Division 2 or Zone 2device has a theoretical ignition risk of 0.01. The 0.05upper bound is based on the Rew and Spenser (1997)model for a "weak" ignition sources as illustrated in Tablell. The most likely value (mode value) was set at 0.02 andreflects the very low number of potential ignition sourcesidentified in the test group. The probability distributionselected is conservative and allows for the wide variety ofcell phone configurations and technologies.8 j/ ean - o.266

0

i0 1 0. 2 0003 004 O.(Mde) Proabiblity of lgnition

Fig. 10 Probability Distribution for an Ignition Event

C. Ta, Ti - Proportion of Time a device is Active andInactive

The probability of a cell phone being active at any giventime is given by the following relationship:

p(Device Active) = Ta / (Ta + Ti)where:

Ta = Time device is activeTi = Time device is inactive

A typical cell phone call lasts between 30 seconds and20 minutes with an average duration of 3 minutes 15seconds. For the purpose of the analysis, it is assumedthat any conversations lasting longer than 20 minuteswould likely be done in a non-hazardous area. Thefrequency of calls will vary with the individual and themodel assumes the interval between calls varies between3 minutes and 8 hours with the average being 20 minutes.A triangular distribution was again used to model the

values of Ta and Ti with the mode values of 3.25 minutesfor Ta and 20 minutes for Ti. The probability distributionsfor Ta and Ti are illustrated in Fig. 11.

Fig. 11 Input Distributions for Ti and Ta

D. Probability Model Simulation

A Monte-Carlo statistical simulation using a LatinHypercube sampling method was done for 500 iterations.The resulting output distribution was derived as illustratedin Fig. 12. The summary statistics associated with thesimulation are provided in Table IV.

0.8 Mean = 1.163578E-060.7 v

> 0.60

- 0.5@ 0.4a) 0.3UL 0.2

0.1

140 3.5 7 10.5p(FE) - Values in 10-6

90% ~~5%

0798 4.4327

Fig. 12 Probability Distribution of a Fire or ExplosionResulting from an Ignition by a Cellular Phone

TABLE IVSummary Statistics

Output Statistics - Fire/Explosion ProbabilityName Min. Mean Max. xl p1 x2 p2

p(FE) | 2.73E- 1.16E- 1.37E- 7.98E- 5% | 43E 95%08 06 05, 08 06

Input Parameters

Name Min. Mode Mean Max.

p(FA) = 1.01 E-04 _ 5.50E-04 9.99E-04

p(IGN) = 1.06E-02 2.OE-02 2.67E-02 4.90E-02Ta = 0.562 3.25 7.834 19.293

Ti = 6.956 20 167.688 471.013

The results indicate that the probability of a fire orexplosion initiated by a cell phone is in the range of0.0789E-06 and 4.4327E-06 with a 90% confidence level,with a mean value of 1.16E-06. This would imply that theprobability of a cell phone causing a fire or explosion in a

Class I, Division 2/Zone2 hazardous location is in the rangeof approximately one in a million.

Vil. CONCLUSION

Cell phones are commonly used in petrochemicaloperations however; government regulations and companypolicies strictly limit the use of cell phones in hazardouslocations. The representative sample of cell phonessubjected to the ISA RP12.12.03-2002 design andperformance criteria failed to pass the requirements for aPEP 2 device. This would imply that all cell phones in thetest group posed an ignition risk in hazardous location.

Further testing and analysis indicated the greatest riskwas associated with dropping a cell phone on a hardsurface. The impact caused the battery to disconnect inthe majority of cases and could potentially create an impactspark under ideal conditions. All other potential ignitionrisks were deemed negligible.

The Monte Carlo model simulation results estimated theprobability of a fire or explosion resulting from the use of acommercial grade cellular phone in a Class Division2/Zone 2 hazardous location as negligible. This conclusionconcurs with several previous studies where cell phoneswere deemed a negligible hazard in gasoline pumpingoperations.

While the research and conclusions of this paperindicate the probability of a cell causing an ignition in aClass I, Division/Zone 2 location are minimal, the authorsdo not suggest the potential hazard can be ignored. Mobilecommunication devices that are third party listed for use inhazardous locations are commercially available and serveto eliminate the risk of ignition. In all case, appropriatesafety measures in accordance with Occupational Healthand Safety (OH&S) regulations, electrical codes and otherregulations must be observed.

IX. ACKNOWLEDGEMENTS

The Authors would like to acknowledge Dave Adams,P.Eng. and Greg Law from CSA International for theirvalued assistance and the use of their explosive testingfacilities in Edmonton, Canada.

X. REFERENCES

[1] ISA RP12.12.03-2002, Recommended Practice forPortable Electronic Products Suitable for Use in ClassI and 11, Division 2, Class I Zone 2 and Class Ill,Division I and 2 Hazardous (Classified) Locations,Research Triangle Park, NC: ISA

[2] Spencer, H.S. & Rew, P.J. 'Ignition Probability ofFlammable Gases (Phase 1)', HSE Contractor ReportRSU8000/081, HSE Books. (1997)

University of Oklahoma, Norman, Oklahoma USA.August 2001.

[4] "Cell Phone Usage at Gasoline Stations." Report toMotorola by Exponent Failure Analysis Associates,Menlo Park, California USA. December 1999.

[5] Institute of Petroleum Technical SeminarProceedings, 'Can Mobile Phones CommunicationsIgnite Petroleum Vapour - Papers from a technicalseminar held in London 11th March 2003' Institute ofPetroleum, London UK. 2003.

[6] US Department of the Interior, Mineral ManagementService, Safety Alert No. 5 'Cell Phone Results in Fire'March, 2002.

[7] US Department of the Interior, Mineral ManagementService, National Safety Alert No. 6 'Cellular Phonesand Other Risks in Classified Areas', November,2002.

[8] NFPA 70, 2002 National Electrical Code, Quincy, MA:NFPA

[9] CSA C22.1-02 Canadian Electrical Code - Part 1,Toronto, ON: CSA

[10] GUIDELINES ON THE APPLICATION OFDIRECTIVE 94/9/EC, Second edition - July 2005.http://europa.eu.int/comm/enterprise/atex/guide/index.htm

[11] API Recommended Practice 505, 'RecommendedPractice for Classification of Locations for ElectricalInstallations at Petroleum Facilities Classified as ClassI, Zone 0, Zone 1, and Zone 2',1 st Edition, November1997

[12] BS 6656:2002 'Assessment of inadvertentignition of flammable atmospheres by radio-frequencyradiation. Guide', British Standards Insititute, London,UK.

[13] IEEE P1725 Draft 7B December 2005, "DraftStandard for Rechargeable Batteries for CellularTelephones" New York, NY: IEEE.

[14] ANSI/ISA 12.00.01-2002 (IEC 60079-0 Mod)"Electrical Apparatus for Use in Class 1, Zone 0,1 &2Hazardous (Classified) Locations: GeneralRequirements" Research Triangle Park, NC: ISA

[15] Institute of Petroleum, 'Model Code of Safe Practice -Part 15, Area Classification Code for InstallationsHandling Flammable Fluids' 3rd Edition, EnergyInstitute (2003), Portland Press.

[3] "Investigation of the Potential for Wireless Phones toCause Explosions at Gas Stations." Center for theStudy of Wireless Electromagnetic Compatibility,

H. VITA

Allan Bozek, P.Eng., MBA graduated from the University ofWaterloo in 1986 with BASc in Systems DesignEngineering and a MBA from the University of Calgary in1999. He is a Principal with EngWorks Inc. providingconsulting engineering services to the oil and gas sectors.Allan is a registered professional engineer in the provincesof Alberta, British Columbia, Saskatchewan and theNorthwest Territories and Nunavut. He has been a memberof the IEEE since 1989. Allan's areas of expertise includehazardous area classification, power systems, heat traceand digital control systems design for large scale industrialfacilities.

Marty Cole has worked for Hubbell Canada for over 25years and has been involved with hazardous locations formuch of that time. He is a member of the CanadianElectrical Code (CEC) Part - Section 18 Subcommitteeand CSA's Integrated Committee on Hazardous LocationProducts. He was vice-chair of the task force that addedthe IEC Zone System to Section 18 and chaired thecommittee that adopted the IEC 60079 Series standards asCSA standards.

Marty is chairman of the Hazardous Location Productssub-section of Electro Federation Canada's (EEMAC)Wiring Products Section, a member of the AdvisoryCommittee for the Objective Based Industrial ElectricalCode (OBIEC), along with a number of other CSA Part 2and IEC standards and technical committees. He hasauthored and co-authored a number of papers and articleson the subject of hazardous locations for the IEEE-PCIC,IEEE-IAS Magazine, EX Magazine and other industrypublications.

Ken Martin graduated from the Southern Alberta Institute ofTechnology in 1982 in Electrical Engineering Technologyand is an active member in The Alberta Society ofEngineering Technology and received his C.E.T. in 1985.Presently after several years of selling in thepetroleum/petrochemical community in Alberta he is anowner and technical sales representative for BrodwellIndustrial Sales Ltd. in Calgary Canada. His primary focusis working with engineering firms and end users in thespecifying of material for electrical equipment and controlsin hazardous and non hazardous locations for over 18years.

ApperSurvey of Major Producers Regarding

1. What is the primary means of communication for personnelworking within a hazardous locations area?

Cell 0Phone

[Radio 80%1)

[Land ][0%

[Other* | 20%

Total 100%*Comments1 - Talking via air waves - no electronic allowed

2. Does your company issue cell phones to operationspersonnel? (if yes answer question 3 otherwise go toquestion 4)

FNo -,

3.

80%

20%

Total || K1

Estimate the percentage of your operations personnel thatroutinelv carrv a mobile cell phone

[0-10 0%

[10-20 25%

20-40 1l.. 50%

[40-60 1l 0%

[80-100 25%

][o%

4. Does your company have a policy regarding the use of cellphones or two way radios in hazardous locations withintheir facilities? (if yes go to question 5, if no go toquestion 6)

100%

< 0% INo F

Total1T00

5. Does the policy permit the use of these devices in facilitieswith hazardous locations?| Yes 11 11 ~~~~~~~~40|~~~ ~ NEo I1H

Tl| ~~~~~~~~~~~~~~Total|

6. Are there specific hazardous location rating requirementsfor the cell phones / radios for used in the facility?

Total 00%

Cell phone Use in Hazardous Locations7. Has your company had any recorded incidents related to

the use of cell phones or radios in hazardous locations?

Zo| Tal 100%I ~~~~~~~~~~~Tota10O%

8. How does your company communicate their cell phone usepolicy to employees and visitors to their facilities?

Part of asafety 0%orientation

Safety [25%handbook

practice [[0

Posted F%signs [ [0%

Other,Please [ 75%Specify*

|____ Total ]i00%]*Comments1-all of above2-All of the above3-Orientation & posted signs

9. Does your company have a policy for operating cell phonesin company vehicles while driving?

No ib 20%

Total |

10. How does your company communicate to visitors whereareas classified as hazardous locations are?

Warningsigns are 40%posted in all 40%areas

AreaClassification 0%drawings inpermit room

[No Policy in 10%place __

Other, 1 _ _ _lPlease 60%Specify* J ___

|___ -Tlotal 100%]*Comments1-Orientation, signs and Operation escorts2-Onsite safety training is mandatory before entry.

Appendix B

Cellular Phone Summary Test ResultsSample Number

GenerationYear of Manufacture

Form Factor

Surface area (cm2)Weight (grams)

Battery Type

Battery Capacity

Battery VoltageHazardous LocationWarning in ManualBattery Short CircuitHazard Warning

2G

1999

Clamshell198.48

156

Li-Ion1600 mAh

3.6V

yes

yes

2

2.5G

1999

Bar

204.5

142.5

Li-Ion

900 mAh

3.6V

yes

3 4

2.5G 2.5G

2001 2001

Clamshell Bar

179.6 186.04

151 108

Li-Ion Li-Ion

850 mAh 750 mAh

3.6V 3.6V

yes yes

5

2.5G

1996

clamshell

179.6

125

Li-Ion

900 mAh

3.6V

yes

6

2G

2001

Bar

204.5

142.5

Ni-MH

900 mAh

3.6V

yes

7 8

2.5G 2.5G2001 2001

Bar flip phone223.1 189.28

133 125

Li-Ion Li-Ion

800 mAh 900 mAh

3.6V 3.6V

yes yes

yes yes yes yes yes yes yes

Visual Analysis

Power On-Off Switch

Vibrator

Micro ContactsBattery SecurityMethod

Battery Connections

External ElectricalConnectionsExternal BatteryCharging Connections

electronic

yes

no

single latch

springterminal

Yes

Yes

electronic electronic electronic

yes yes yes

no no nosingle dual latch slnglelatchlac

spring IsOspring plugterminal loaded connectiorterminalsflatYes Yes Yes

electronic

yes

nosinglelatch

springn terminal

electronic electronic electronic

no yes yes

no no nosingle dual latch single latchlatch

spring spring springterminal terminal terminal

Yes No Yes Yes

No No No No No No No

Tests

Drop Test FailVisual Damage noneInspectionOperational test after operatedDrop testBattery Short Circuit N pr

(Visual) No SparkBattery Short Circuit -3.6(Temp Rise IC)Vibrator Test (Test No IgnitiorChamber)

Fail Fail Fail Failexterior

none none none damage

operated operated operated operated

No Spark No Spark No Spark No Spark

-3 -0.5

No Notn Ignition Tested

-1 -0.8

No Ignition NonIgnition

Fail Fail Pass

none none none

operated operated operated

No Spark No Spark No Spark

-1.4 -0.7

N/A NotTested

-0.4

No Ignition