REMEMBER! If you work with Lasers you are responsible for your own safety and for the safety of those around you.

Christopher SmithCollege Laser Safety Officer (LSO)School of PhysicsTrinity College Dublin

Ext: 3649 / 2167Email: chris.smith@tcd.ie

Url: www.tcd.ie/Physics/opticslab/Laser_safety/Laser_safety.phpOr simply search for laser safety trinity college in your browser

LASER SAFETY

1. Legislation 2. Training and Registration 3. Laser Radiation Properties4. Laser Hazards and Injury 5. Power and Energy6. Maximum Permissible Exposure7. Laser Classification8. Controls and Protection9. Laser Safety Eyewear10.Labels and Signage11.Safety and the University Environment12.Safety Precautions and Risk Assessment 13.Emergency procedure

LASER SAFETY

You may discover a culture of complacency Don’t be drawn in, protect your eyes

Peer Pressure in the Lab

Even relatively small amounts of laser light can lead to permanent eye injuries, therefore the sale and usage of lasers is subject to government regulations. Moderate and high-power lasers are potentially hazardous because they can seriously damage the retina of your eye, or even your skin.

EU Directive 2006/25/EC (Ref 114): on the minimum health and safety requirements regarding the exposure of workers to risks arising from artificial optical radiation

Ireland Health and Safety Authority (HSA): Safety, Health and Welfare at Work act 2005 amended 2010, Control of Artificial Optical Radiation at Work Regulations 2010 (S.I. No. 176 of 2010) available at http://www.hsa.ie/…

On February 5 2014, the European Union issued a “decision ... on the safety requirements to be met by European standards for consumer laser products." The decision will severely restrict or ban European consumer access to Class 3R, 3B and 4 lasers. For lasers emitting visible beams, this would restrict or ban consumer laser products with an output of 1mW or greater.

LASER SAFETYLegislation

• to identify the risks and ensure that workers are not exposed to levels of artificial optical radiation in excess of the exposure limit values.

• to take action to eliminate or control these risks.

LASER SAFETYLegal requirement

Laser User(s) • Follow College safety procedures and rules• Carry out risk assessments related to your experiment• Apply controls to reduce risk

College• Provide you with suitable information and training• Provide you with safe infrastructure and equipment

RESPONSIBILITIES

Register of all LASERS

• Class of Laser• Location • Responsible person in charge

Register of all DESIGNATED LASER USERS

• Position • Name • Supervisor / Group• School / Department• e-mail address

College Register

All personnel wishing to work in areas containing Class 3R, 3B and Class 4 lasers must

Attend the course given by the LSO Complete the registration process Be a Registered Laser User

All personnel working with lasers must

Be aware of the hazards Complete a risk assessment before commencing work Take appropriate precautions Take appropriate action in the event of an incident

Training and Registration

1. Log on to BLACKBOARD at https://mymodule.tcd.ie

2. Enrol onto the Laser Safety Module

To Complete the registration process you must

Any issues, please email me at chris.smith@tcd.ie

3. Do the online assessment

Training and Registration

Typical Properties Coherent composed of waves with same relative phase High Power Density high incident power or energy per unit area

Monochromatic narrow spectral bandwidth (one colour)

Continuous Wave (CW) constant output power (Watts)

Pulsed output energy (Joules) or average Power (Watts)

Collimated beam highly directional (Low angular divergence)

t

t

λ

P

P

I

Laser Radiation Properties

Retinal injuries are usually larger than the focused spot due to secondary effects. Extremely small injury to the retina can significantly damage vision.

Pupil diameter is about 2mm giving an area ≈ 3mm2

~ 1000 W/m2 or 0.1 W/cm2 hitting the surface of the earth

Approximate 200mm diameter spot on retina

E ≈ 10 W/cm2

Approximate 10mm diameter spot on retina

E ≈ 1200 W/cm2

1mW enters the eye

Irradiance E

Due to the focusing effects of the eye the irradiance of a laser beam can be increased up to a factor of 100,000 on the retina!

Low Divergence BeamEven a very low power laser is a potential hazard; the eye will focus a laser beam (400-1400nm) to a very small spot, ~10 micrometers. For example a 1-milliwatt beam produces a retinal irradiance value on the order of 1200 W/cm2. Direct viewing of the sun produces an irradiance at the retina of approximately 10 W/cm2.

Irradiance Comparison

Laser radiation Eye: corneal and, or retinal burns,

lens damage, cataractsSkin: burns, accelerated aging, cancer

Electrical HazardsHigh current: power supplies (large capacitors)

Chemical HazardsMaterial Emissions: particulate and gaseous

materials (vaporised targets, reaction products)

Secondary HazardsExplosion: high gas pressure arc lampsFire: combustible material in vicinity of beam

Laser Hazards

Thermal effectsOptical energy is absorbed thus the temperature of tissue increases resulting in tissue burns. This energy can result in a burn injury to an area extending further around the incident beam site with increased time of exposure. Significant tissue injury can occur with only milliseconds of exposure.

Acoustical effectsAcoustical or thermomechanical effects occur when the tissue is heated very rapidly in only nanoseconds or less of exposure inducing a mechanical shockwave through the tissue. The liquid component of the tissues may evaporate into a hot gas with extremely high temperatures. The phase changes are so rapid that they are explosive and the cells rupture.

Photochemical effectscan be the direct result of specific wavelength absorption resulting in chemical changes in exposed tissues, typically in the UV range. This photochemical reaction is responsible for damage at relatively low levels of exposure where duration of exposure is more significant. The skin, the lens of the eye, and to a lesser extent the retina may show irreversible changes induced by prolonged exposure to moderate levels of UV radiation.

Mechanism of Injury

Wavelength Range RISKMid UV 180 – 315 nm CorneaNear UV 315 – 400 nm LensVisible 400 – 700 nm RetinaNear IR 700 – 1,400 nm RetinaMid-Far IR 1,400 nm – 1 mm Cornea -

Lens

Skin is far less vulnerable to injury since the focusing effect does not occur.

The retina is not responsive to radiation outside the visible spectrum, 700 – 1,400 nm. No sensation results in the eye when exposed to this wavelength range, resulting in a much greater hazard from lasers operating in the Near IR.

Wavelength Range RISKMid UV 180 – 315 nm CorneaNear UV 315 – 400 nm LensVisible 400 – 700 nm RetinaNear IR 700 – 1,400 nm RetinaMid-Far IR 1,400 nm – 1 mm Cornea -

Lens

Visible 400 – 700 nm RetinaNear IR 700 – 1,400 nm Retina

Ocular HazardLight Absorption

by the Different Ocular Tissues

Photoablation is the absorption of incident photons and subsequent breakdown and release of biological material. Excimer lasers in the ultraviolet with nanosecond pulses focused with power densities in the order of 108 W/cm2 can produce this photoablative effect. Ultraviolet radiation is strongly absorbed by biomolecules, in depths of just a few micrometres.

Source: http://www.lbl.gov/ehs/safety/lasers/bioeffects.shtml

Thermal damage occurs because of the conversion of laser energy into heat. With the laser’s ability to focus on points a few µm or mm in diameter, thus high power densities can be spatially confined causing heat damage to tissues. Depth of penetration into the tissue varies with wavelength of the incident radiation, thus determining the amount of tissue removal and bleeding.

Large retinal burn from 1 watt, 445nm (blue) laser.

Eye Injury

The onset of a headache shortly after exposure, excessive watering of the eyes, sudden appearance of tiny spots, or threads, that drift in your field of vision (floaters).

Minor corneal burns cause a gritty feeling, like sand in the eye The exposure to a visible laser beam can be detected by a bright colour

flash of the emitted wavelength and an after-image of its complementary colour (e.g., a green 532 nm laser light would produce a green flash followed by a red after-image).

Exposure to a near infrared beam 700 to 1400 nm is especially hazardous. There is no blink reflex initiated and may initially go undetected because the beam is invisible and the retina lacks pain sensory nerves. The onset of symptoms may occur a while after the incident.

Acoustical or thermomechanical retinal damage may be associated with an audible "pop" at the time of exposure. Visual disorientation due to retinal damage may not be apparent to the operator until considerable thermal damage has occurred.

Eye Injury Symptoms

A postgraduate student sustained a serious eye injury from an Nd:YAG laser. He had worn his protective eyewear in the afternoon when he set up the experiment, but when he returned to take some data after a break, he did not bother putting the eyewear back on because, he felt, there were no exposed beams that posed any danger. As he made a slight adjustment to a power-meter, he saw a flash and heard a loud popping sound. He had sustained a serious injury to his left eye. The student experienced some vision impairment months after the accident. Moreover the incident led to a prolonged investigation and a significant decline in funding for the research group. From an Article in Photonics Spectra 2005, In Laser Safety, Little Mistakes Can Have Big Consequences, Kenneth L. Barat, Lawrence Livermore National Laboratory

Accident Case Study

1. Unanticipated eye exposure during alignment. 2. Misaligned optics and upwardly directed beams. 3. Available laser eye protection was not used. 4. Equipment malfunction. 5. Improper method of handling high voltage. 6. Intentional exposure of unprotected persons. 7. Operators unfamiliar with laser equipment. 8. No protection provided for associated hazards. 9. Improper restoration of equipment following servicing. 10. Incorrect eyewear selection and/or eyewear failure. 11. Accidental eye / skin exposure during normal use. 12. Inhalation of laser-generated fume & viewing of secondary radiation (UV, blue light). 13. Laser ignition of fires. 14. Photochemical eye or skin exposure.

Visible and near-infrared laser injuries account for more than 80% of all the reported incidents. Pay attention to alignment procedures and always wear protective eyewear!

Top 14 AccidentsRockwell Laser Industry's top 14

Reported Causes of Laser Related Injuries

All high power lasers can cause skin burns!Ultra Violet radiation (UV): is a particular source of danger even at low power Ultra Violet Sources in the Lab: include Lasers, e.g. optical parametric amplifier (OPA) and UV lamps e.g. xenon Lamps

UV C (180-280 nm) Absorbed in Ozone layerUV B (280-315 nm) Deep strata of skin at riskUV A (315-400 nm) Tanning, Skin at risk

Effects of exposure on skin mild erythema (sunburn) accelerated skin ageing skin cancer.

Skin Hazards

The power of a laser is measured in Watts (W) and often reported in terms of milliwatts (mW) for relatively low powered systems. This is referring to the optical power output of the laser beam, which is the constant output power of continuous wave (CW) lasers, or the average power of a pulsed or modulated lasers.

The energy of a laser typically reported in nanoJoules to milliJoules (nJ, µJ, mJ) refers to the output of a pulsed laser where the pulse energy (Q) is the laser’s peak power (PPEAK) multiplied by the laser pulse duration (tPULSE):

Q = PPEAK x tPULSE

The average power of a pulsed laser (PAVG) is the pulse energy (Q) multiplied by the laser repetition rate (Rep), in Hertz. i.e. 1 Watt =1 joule per second

PAVG = Q x Rep

P

time

tPULSE

P

PAVG

time

1 / Rep

PPEAK

Continuous Wave Laser Pulsed Laser

Power and Energy

For example, an Excimer laser might have a 10ns pulse, an energy of 10 mJ per pulse, and operates at a repetition rate of 10 pulses per second (Hz). This laser has a peak power of:

PPEAK = 10mJ / 10ns = 1MWand an average power of:

PAVG = 10mJ x 10Hz = 100mWThe pulse width can be very short (i.e. picoseconds or femtoseconds) resulting in very high peak powers with relatively low pulse energy, or can be very long (i.e. milliseconds) resulting in low peak power and high pulse energy, while each of these conditions might have similar average power levels.

Power and Energy

CW Laser: optical power of 10mW Energy in 0.25 sec (blink reflex)

Pulsed Laser: 2.5x10-3 Joules per 10ns pulse

3 310 10 0.25 2.5 10W s Joules

352.5 10 2.5 10

10JPeak Power W

nS

Quarter of a Megawatt (0.25MW) in 10ns

Compare CW with Pulsed

MPE depends on: wavelength exposure time pulse duration tissue at risk (ocular or skin) spatial distribution of the beam

MPE is that level of laser radiation to which persons may be exposed without suffering immediate or long term adverse effects. Usually 10% of the dose that has 50% chance of doing damage. Measured in radiance in W/cm2 or radiant exposure in J/cm2

The MPE values are equivalent to the Exposure Limit Values (ELV) except in some special cases, the only significant difference is that ELVs are mandatory levels which must not be exceeded

MPE: Maximum Permissible Exposure

Assessing the Optical Safety

The Accessible Emission Limit (AEL) is the primary measurement of a laser’s hazard potential known to cause a biological effect in a target tissue. The AEL defines the maximum total power or energy of laser radiation permitted within a particular laser class that can be emitted……… • in a specified wavelength range • In a specified exposure time • through a specified aperture stop • at a specified distance

• It is not applicable to CLASS 4 lasers as no upper limit for this class. • The AEL values are determined using the MPEs.

Each laser must have a classification label and hazard warning notice

Laser ClassificationClassification indicates the level of

laser beam hazard

International Electrotechnical Commission (IEC) document 60825-1 is the primary standard that outlines the classification of laser products

CLASS Label Implication

1Safe, typically inherent or by design. Lasers are embedded with interlocks. All wavelengths. E.g. Laser printer, DVD/CD players and, confocal microscopes

1Ctypically medical lasers where laser radiation is intended to be applied to a particular target tissue. There are safeguards that prevent leakage of laser radiation in excess of an equivalent Class 1 laser.

1MSafe only if optical components such as lenses are not used, must be either collimated with large beam diameter or highly divergent. E.g. fibre-optic communication systems

2Safe within normal use. Low power visible 400-700nm. CW or pulsed <1mW natural eye protection – blink reflex <.25s. E.g amusement laser guns, laser pointers and barcode scanners.

2MSafe as with class 2. visible low power , but potentially hazardous when optical components are used, must be either collimated with large beam diameter or highly divergent. E.g. level and orientation instruments for civil engineering applications, theodolites.

3RSafe when used in normal operationhandled carefully. Low-medium power 1–5 mW potentially hazardous. e.g. laser pointers and alignment lasers.

IEC Laser Classifications

CLASS Label Implication

3BMEDIUM POWER from 5mw to 500mW all wavelengths hazardous for direct beam viewing and specular reflections viewing of diffuse reflections normally safe. distance >13 cm and duration < 10 s . Examples: Diode lasers > 5mW

4

HIGH POWER >500 mW all wavelengths hazardous for direct beam viewing, specular reflections and diffuse reflections (i.e. radiation reflected over a wide angular range). Example. Coherent MIRA femtosecond pulsed Laser ~500mW

Also fire and skin hazards: beam can cause ignition of combustible material, paper, clothes, plastic, chemicals, etc.

IF YOU DO NOT KNOW THE CLASS OF A LASER ASSUME IT IS CLASS 4!

International Electrotechnical Commission (IEC) document 60825-1 is the primary standard that outlines the classification of laser products

IEC Laser Classifications

OLD NEW HAZARD LEVEL

1

1 Safe because of enclosure but may have embedded high powered lasers

1C Safe when used only as intended on target tissue

1M Safe provided optical instruments not used to viewAvoid using magnifying lenses, telescopes, microscopes etc

22 Visible lasers. Safe for accidental exposure (< 0.25s)

Avoid staring into the beam

2M Visible lasers. Safe for accidental exposure (< 0.25s)providing optical instruments not use. Avoid staring into the beam

3A & 3B* 3R Not safe. Low risk Prevent direct eye exposure

3B** 3B Hazardous. Viewing of diffuse reflection may be safe.Prevent eye and skin exposure

4 4 Hazardous. Viewing of diffuse reflection also hazardous. Fire risk. Prevent eye and skin exposure

Any laser product of a given Class may contain 'embedded' lasers which are greater than the Class assigned to the product, but in these cases engineering controls (protective housings and interlocks) ensure that human access to radiation in excess of product Class is not possible. Also you may see laser classes marked in Roman numerals.e.g. IIIB

Classification; Old and New

1. Engineering Controls• Design the experiment/lab in such a way that dangerous exposure cannot happen. Reduce power during alignment• Use beam enclosures and place beam blocks where possible• Ensure all optics and mounts are securely fixed to optical table. Many incidents happen with an accidentally deflected beam• Use a designated area with interlocks and warning lights on the entrances

2. Administrative Controls• Laser Safety Training• Designated Areas • Good Signage

3. Personal Protection• Safety Eye wear, Protective clothing• Awareness and good sense

– do I need to be here? – what are others in the laboratory doing?

Three Lines of Defence

Control Measures Requirement

Laser Classification

1 1M 2 2M 3R 3B 4Designated Laser Area (DLA) n/a n/a n/a n/a n/a

Remote Interlock on DLA n/a n/a n/a n/a n/a

Key Control n/a n/a n/a n/a n/a Emission Indicator n/a n/a n/a n/a Beam Stop/Shutter n/a n/a n/a n/a n/a Beam Terminator n/a n/a Beam Path (below eye level, parallel and close to table)

n/a

Beam Enclosure n/a n/a n/a n/a Eye protection n/a n/a n/a n/a Laser Safety Training n/a n/a n/a n/a n/a Door Warning Signs n/a n/a n/a n/a

Control Measures

Optical density (OD)

10log HODMPE

Attenuation Factor (H/MPE)

OD

10 1100 2

1,000 310,000 4

100,000 51,000,000 6

Optical density simply tells you how much or how little light is transmitted through a filter at the laser wavelength. It does not account for the damage threshold of the filter material!For example: Consider and ocular MPE ≈ 1mW and a Filter OD = 6 we may assume wrongly that the eyewear protects against 1mW x106 = 1kW but the material may be easily destroyed when placed in the beam and offer little or no protection.

H = the anticipated worst case radiant exposure and is measured in the same units as the Maximum Permissible Exposure, W/cm2 or Joules/cm2

Laser Safety Eyewear

*D63 diameter is when 63.2% (1/e cut-off) of the total power is contained in a variable aperture

LB Rating Specifies damage threshold of material at Maximum power or energy density. Must be able to withstand a direct hit for a period of > 5 seconds in Continuous

Wave mode or for 50 pulses. This Scale number should give reasonable comparability of similar laser safety

products. We do not need to worry about calculating the MPEs because this has already

been taken account of in the maximum power / energy densities specified for each LB number.

EN207

Beam Diameter D63* Exposure time Labelling

1998 2mm 10s or 100 pulses

L

2010 1mm 5s or 50 pulses LB

Another standard EN208 applies to Visible lasers only (ie 400 - 700 nm wavelength range) and is a standard used for alignment eyewear where sometimes it is necessary to be able to see where the beam is for purposes of setting up. The hazard is reduced to below the Class 2 limit . It uses the R rating, e.g. R3 instead of LB3 (not to be confused with the emission type R - Short Pulsed)

Laser Safety EyewearEuropean standard EN207 1998/2010

900-1100 D LB 10 LV DIN CE S

Wavelength (nm)

Laser Type

(DIRM)Protection

levelManufacturin

g codeCompliance

EC type approval

Mechanical robustness

900-1100 D LB 10 LV DIN CE S

Wavelength (nm)

900-1100

LaserType

(DIRM)

D

Protection level

LB 10

Manufacturing code

LV

Compliance

DIN

EC type approval

CE

Mechanical

robustness

S

Temporal mode of the laser beamD - Continuous wave (>0.25s)I - Pulsed (1ms to 0.25s)R - Short Pulsed (1ns to 1ms)M - Ultra short pulsed (< 1ns)

LB 10: Damage protection rating OD implicit in the LB number OD>10 over the range 900-1100nm

Laser Safety EyewearLabelling of Eyewear Based on EN207:2010

Max power density (W/m2) & Energy Density (J/m2 ) in specified wavelength Range and for Pulse duration in seconds (s)

EN207180 -315 nm 315 -1400 nm 1400 nm -1000 μm

W/m2 J/m2 W/m2 W/m2 J/m2 J/m2 W/m2 J/m2 W/m2

D I,R M D I,R M D I,R MScale Number

T >3x10-4 s 10-9 s to 3x10-4 s <10-9 s >5x10-4 s 10-9 s to

5x10-4 s < 10-9 s 0.1s 10-9 s to 0.1s < 10-9 s

LB1 10-1 0.01 3x102 3x1011 102 0.05 1.5x10-3 104 103 1012

LB2 10-2 0.1 3x103 3x1012 103 0.5 1.5x10-2 105 104 1013

LB3 10-3 1 3x104 3x1013 104 5 0.15 106 105 1014

LB4 10-4 10 3x105 3x1014 105 50 1.5 107 106 1015

LB5 10-5 102 3x106 3x1015 106 5x102 15 108 107 1016

LB6 10-6 103 3x107 3x1016 107 5x103 1.5x102 109 108 1017

LB7 10-7 104 3x108 3x1017 108 5x104 1.5x103 1010 109 1018

LB8 10-8 105 3x109 3x1018 109 5x105 1.5x104 1011 1010 1019

LB9 10-9 106 3x1010 3x1019 1010 5x106 1.5x105 1012 1011 1020

LB10 10-10 107 3x1011 3x1020 1011 5x107 1.5x106 1013 1012 1021

10W CW laser 1064 nm, 4 mm beam diameter: the power density ~8x105 Wm-2

Round the Power up never down!

Laser Safety EyewearChoosing Eyewear Based on EN207:2010

Check carefully whether the marking on the laser safety eyewear gives you the appropriate protection required for the laser you are using.

1. Appropriate wavelength(s)?2. Appropriate type? Pulsed or Continuous Wave?3. Appropriate for alignment (R) or full protection (LB)

Do not assume just because the eyewear is in a particular location or it is handed to you that it is correct.

It is your personal responsibility to always check and use the correct laser safety eyewear!

Laser Safety Eyewear

Warning Labels and Signage

VISIBLE AND/OR INVISIBLE LASER RADIATION

Contact: ( person in charge of lab/laser and contact number)

Danger

AVOID EYE OR SKIN EXPOSURE

Laser Type: PulsedWavelength: 355 nmAverage Power: 7 Watts

CLASS 4 LASERLaser Safety Officer: chris.smith@tcd.ie

• 100% Protection?• Not possible to have industrial safety levels – fully enclosed systems• Apply the ALARA principle: risk should be As Low As Reasonably

Achievable!

• Multiple user access• There can be more than one laser in use in the laboratory• there can be more than one wavelength in use in the laboratory at

one time

• Versatile systems • Changing wavelengths• Re-alignments• Repairs Safety Awareness

is CRUCIAL!

Working in a UniversityThe Teaching and Research Environment

What do we need to do?• Identify hazards (potential for harm) • Assess risk from these hazards• Determine and implement relevant safety measures• Assess residual risk – refine control measures

Risk AssessmentAction prior to proposed experiment

Why do risk assessments?• There is a legal obligation under the 2005 Safety, Health and Welfare

at Work act. • There is a moral obligation to ensure the safety of everyone in the

work environment.• There are Economic reasons too, accidents cost money, productivity,

damage and injury.

Safety PrecautionsUser best Practice

The Big Bang Theory, “The Work Song Nanocluster” E18/S2 2009 CBS

Eye protection: Safety eyewear / Goggles Intelligent behaviour: Never look into the laser output aperture Indirect Viewing: use viewing cards and infrared viewers during alignment Beam path: short as possible & directed away from door. Beam stop: terminate beam at end of useful path. Beam level: Don't place beam at eye level. Beam enclosure: Intra-beam viewing prevented. Don’t wear reflective items: watches or jewellery. Stabilise components: Laser and optical components securely fixed to table. Wear: Protective clothing. Key control: Removed from power supply when laser shut down. Multiple lasers: partitions, screens, multi-wavelength safety glasses.

Safety PrecautionsUser best Practice

Door Wide OpenNo Interlock!

Goggles only for Limited Wavelengths!

Untrained, Unregistered personnel in the lab!

DON’T GET MESTARTED

HERE!

The Big Bang Theory, “The Holographic Excitation" E5/S6 2012 CBS

Clutter, Trip Hazards!

What’s Wrong Here?Big Bang or Big Mistake?

• Immediate medical attentionCollege emergency number Ext. 1999 or 01 896 1999Accident & EmergencyRoyal Victoria Eye and Ear HospitalAdelaide RoadDublin 2Tel: 01-7088 535

• Seek assistance immediately you could be already or going into shock.

• Power the laser down if you are able to do so safely or ask another registered laser user familiar with the system to help. Ask them to write down the power and wavelength of the laser for the hospital.

• Do not use the laboratory or disturb the equipment until after the accident has been investigated.

• Report all accidents to the Laser Safety Officer and the School/Department Safety Officer

Emergency Procedure

Christopher SmithEmail: chris.smith@tcd.ie Ext: 3649 / 2167 url: http://www.tcd.ie/Physics/opticslab/Laser_safety/Laser_safety.phpOr just type laser safety trinity into a search engine

If you are in doubt or you do not feel youare working with safe practices or equipment

Contact your laser safety officer

It is your right to work safely no matter the cost or inconvenience; it’s cheaper than an eye

Thank you for your attention

COMPLACENCY IS YOUR ENEMY!

FINALLY!