Effect of Room Ventilation Rates in Rodent Rooms with Direct-Exhaust IVC Systems

Roger Geertsema DVM, DACLAM, DAVCPM

Background

• Vivarium with Individual Ventilated Cages (IVC) for rodents with cage exhaust directly ventilated out of room

• Tecniplast IVC with positive pressure cages (70% cage exhaust rate)

Specific Aims• Can room ventilation rates be safely lowered in rodent

rooms utilizing direct exhaust individually-ventilated caging (IVC)

• Air quality within the room that could have an occupational health or animal wellbeing effect

• Changes in intracage environmental conditions that could impact animal wellbeing or complicate research results

Study Design

8 rodent rooms 7 mouse rooms 1 rat room

2 ventilation rates Low: 5 – 6 ACHHigh:

10 – 12 ACH  Density of Room in cages/sq.ft. (# of cages in room)

PeriodRats (140)

1.2(280)

1.2(540)

0.8(175)

0.6(190)

0.6170)

0.2(65)

0.1(25)

1 High Low Low High High Low Low High

2 Low High High Low Low High High Low

3 High Low Low High High Low Low High

4 Low High High Low Low High High Low

Air Flow

Room Volume 2800 cu.ft.

Room Pressure Differential Positive

Cage Pressure Differential Positive

Room Ventilation Rate High Low

CFM Supply 500 250

ACH 10.7 5.3

CFM from Racks (2) 100 100

CFM for Pressure Offset 100 100

CFM from Room Exhaust 300 50

Ventilation Cost ($3.50/cfm) $1750/year $875/year

Study Design

Compare Low vs. High room ventilation rates for:• Room CO2 (difference between supply - exhaust air)• Room Dew Point Temperature (difference between

supply - exhaust air)• Room Mouse Allergen (Mus m1)• Room Endotoxin• Intracage Ammonia, CO2, Temperature, and Humidity• Create a controlled spill of EtOH in room

• Evaluate the peak level and amount of time to return to baseline at Low vs. High ventilation

Demand-Controlled Ventilation (DCV)

• Computer controlled Phoenix valves in supply and room exhaust

• Monitoring of room air quality for temperature, dew point temperature, CO2, dust particles, and Total Volatile Organic Chemicals (TVOC)

• Sample taken every 15 min. from room exhaust, not the cage exhaust

• Ability to increase ventilation rate based on monitoring parameters

*

Rats 1.2 1.2 0.8 0.6 0.6 0.2 0.10

20

40

60

80

100

120

140

Room CO2 Level - Difference between Supply Air

High

Low

Density of Room (cages/sq.ft.)

CO2

(ppm

)

Rats 1.2 1.2 0.8 0.6 0.6 0.2 0.10.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Room Dew Point Temperature - Difference between Supply Air

HiLo

Density of Room (cages/sq.ft.)

°F

0.6 1.20

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Room Level of Mus M 1 Allergen

High

Low

Density of Room (cages/sq.ft.)

ng/m

3

0.6 1.2

-0.005

5.20417042793042E-18

0.005

0.01

0.015

0.02

0.025

0.03Room Level of Endotoxin

High

Low

Density of Room (cages/sq.ft.)

ng/m

3

A B C D800

900

1000

1100

1200

1300

1400

CO2 Level within Cages

Hi

Lo

Cage

ppm

A B C D0

5

10

15

20

25

30

35

Ammonia Level Within Cage at 2 Weeks

Hi Lo

Cage

ppm

A B C D0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Temperature Difference Between Cage & Room

Hi

Lo

Cage

°F

Period 1 Period 2 Period 3 Period 430%

40%

50%

60%

70%

% Humidity within Cage

Hi

Lo

-5 10 25 40 55 70 850

1

2

3

4

5

6

7

8

9

Room EtOH Level After a Spill

HighLow

Minutes After Spill

ppm

*

-5 10 25 40 55 70 850

1

2

3

4

5

6

7

8

9

EtOH Level After a Spill with Demand-Controlled Vential-tion (DCV)

High - without DCV

Low - without DCV

Low - with DCVpp

m

Minutes after spill

Summary of Results

• Low ventilation rate:• Slightly increased level of CO2

• Slightly increased Dew Point Temperature• Increased time to clear a VOC spill (demand-controlled

ventilation will mitigate this)• No difference in:

• Mus m1• Endotoxin• Intracage ammonia, CO2, temperature, and humidity

Conclusions

• It is safe to lower the room ventilation rate to 5 – 6 ACH both for human workers and animals with a direct exhaust IVC system that is properly designed and maintained - This may not apply to all IVC systems• Although some statistically significant effects were

observed, air quality still well within acceptable guidelines (ASHRAE limit for CO2 in room air is 1000 ppm)

• With a demand-controlled ventilation system, the air is cleared of a spilled VOC faster (assuming the VOC is able to be detected by the system)

Acknowledgements

• ACLAM Foundation Grant• Dr. Lindsell, Matthew Gudorf, Alvin Samala,

Scott Smith, & Michael Phelan