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:
High:
5 – 6 ACH
10 – 12 ACH
Period
Rats
(140)
Density of Room in cages/sq.ft. (# of cages in room)
1.2
1.2
0.8
0.6
0.6
0.2
(280)
(540)
(175)
(190)
170)
(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
Room CO2 Level - Difference between Supply Air
140
*
120
High
CO2 (ppm)
100
Low
80
60
40
20
0
Rats
1.2
1.2
0.8
0.6
0.6
Density of Room (cages/sq.ft.)
0.2
0.1
Room Dew Point Temperature - Difference between
Supply Air
1.4
1.2
Hi
Lo
1.0
°F
0.8
0.6
0.4
0.2
0.0
Rats
1.2
1.2
0.8
0.6
0.6
Density of Room (cages/sq.ft.)
0.2
0.1
Room Level of Mus M 1 Allergen
0.6
0.5
ng/m3
High
0.4
Low
0.3
0.2
0.1
0
0.6
1.2
Density of Room (cages/sq.ft.)
Room Level of Endotoxin
0.03
0.025
High
ng/m3
0.02
Low
0.015
0.01
0.005
0
0.6
1.2
Density of Room (cages/sq.ft.)
CO2 Level within Cages
1400
Hi
1300
Lo
ppm
1200
1100
1000
900
800
A
B
C
Cage
D
Ammonia Level Within Cage at 2 Weeks
35
30
Hi
ppm
25
Lo
20
15
10
5
0
A
B
C
Cage
D
Temperature Difference Between Cage & Room
6.0
5.0
Hi
Lo
°F
4.0
3.0
2.0
1.0
0.0
A
B
C
Cage
D
% Humidity within Cage
70%
60%
Hi
Lo
50%
40%
30%
Period 1
Period 2
Period 3
Period 4
Room EtOH Level After a Spill
9
8
7
High
Low
ppm
6
5
4
3
2
1
0
-5
10
25
40
Minutes After Spill
55
70
85
9
EtOH Level After a Spill with Demand-Controlled
Ventialtion (DCV)
ppm
8
7
High - without
DCV
6
Low - without
DCV
5
Low - with
DCV
*
4
3
2
1
0
-5
10
25
40
55
Minutes after spill
70
85
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