Ammonia and carbon dioxide concentrations in disposable and

reusable static mouse cagesJerald Silverman, DVM, MPS, DACLAM, David W. Bays, BS, LATG & Stephen P. Baker, MScPH

The performance of static mouse cages depends upon the cage's ability to dissipate carbon dioxide and ammonia.

Reusable and disposable cages

Reusable Cage

Gas Sampling Ports

Disposable Cage

Gas sampling ports

Inside view of a gas Sampling port with protective

cover.

Cage location on rack

Dispose

Dispose

Reuse

Reuse

Reuse

Dispose

CD-1™ MouseCrl:CD1(ICR)

Retired breeder females with averageweights of 47 to 48 grams.

Drager CMS Analyzer

Ammonia (ppm)0.2 – 5.0 2.0 – 50 10 – 150

100 – 2,000

Carbon dioxide (ppm)200- 3,000

1000 – 25,000

Intra-cage Temperature & Humidity

Typical placement of data logger

Room Temperature & Humidity

Mean Intracage Temperature &

Relative Humidity

Mean low (oC)

Mean high (oC)

Temperaturerange (oC)

Mean low RH (%)

Mean high RH (%)

RH range (%)

Study period 1 Disposable 21.8 23.8 21.3-24.0 48.6 83.1 45.1-85.2 Reusable 22.4 24.8 21.9-25.2 43.9 86.0 35.7-87.2Study period 2 Disposable 22.5 23.8 21.9-25.2 48.4 83.1 38.3-87.2 Reusable 21.8 24.5 21.0-24.8 57.9 84.2 54.0-87.2

ConclusionsNeither cage type was particularly effective in controlling what empirically is considered to be high levels of ammonia and CO2. Nevertheless, without a clear understanding of the potential adverse health effects of given levels of intracage ammonia and CO2 on laboratory animals and without a consensus on maximal desirable intracage levels of these gases, only estimates can be made about the recommended frequency of cage changing. We suggest, based only on human exposure guidelines and a conservative reading of the available veterinary literature, that intracage levels of 50 ppm of ammonia should lead to cage changing. In the current study that would translate to approximately twice weekly cage changing. The CO2 levels rose so quickly and the effects of CO2 on laboratory animals are so varied that it is quite difficult to recommend any cage changing frequency that is based on CO2 level alone.