Properly Sizing an Autoclave Chamber for Your Animal Lab

Steam sterilization is routinely used in animal laboratories for two reasons: 1) to sterilize animal cages in order to create a pathogen-free housing environment and 2) to properly dispose of harmful waste products. Since autoclaves are essential for everyday laboratory operation, it is important to select a chamber size with enough capacity to meet the lab’s demand for cage and waste processing. Under-sizing the autoclave will leave it insufficient to meet the lab’s demands while an oversized autoclave takes up valuable lab space and carries a higher upfront cost.

An animal lab facility should consider two primary factors before making a sterilizer purchasing decision:

  1. The facility’s Animal Biosafety Level requirement
  2. The number of animal cages that need to be processed

What are my Animal Biosafety Level requirements?

The ABSL rating of a particular animal lab can influence cage sterile processing procedure, which impacts throughput. For example, consider the process flows for two laboratories, one ABSL-1 and one ABSL-3, changing out the same amount of cages per week.

ABSL-1 Cage Processing Pocedure ABSL-2 or ABSL-3 Cage Processing Procedure

Although both labs are processing the same amount of cages, the ABSL-3 laboratory has over twice the sterilization demand. In addition to autoclaving the fully assembled cages (the final step), an ABSL-3 lab must also perform two additional autoclave cycles: one for the cages before washing and one for the soiled bedding. It is important to note that after emptying the soiled cages in a biological safety cabinet (BSC), they can be nested together (see Figure 4) to allow more cages to fit in the autoclave chamber. After washing, the cages are sterilized fully assembled with bedding (see Figure 3). 

How many cages need to be processed?

The first step in determining the required autoclave chamber size is figuring out how many cages are changed at a time. This estimation depends on the total number of animals in the facility and their size.[1]

After you have established an estimate for how many cages need to be changed, consider that a standard mouse cage is approximately 7.5” x 11.5” x 5”. From here, you can approximate chamber dimensions to handle the amount of cages you need to sterilize per load. For example, 80-96 fully assembled mouse cages can comfortably fit in an autoclave with chamber size of 36” x 48” x 72” (see Figure 3).

Figure 3 - Assembled Cages

Figure 3: Assembled Cages

Figure 4 - Nested Cages

Figure 4: Nested Cages

It is essential for an animal laboratory to select an adequate chamber volume for their autoclave. If the volume is too small, the lab will be limited to how many cages they can process per week. On the other hand, purchasing an unnecessarily large chamber is a needless expense. Analyzing cage processing procedures and estimating how many total cages are used can give animal labs a good estimate of their required autoclave chamber size.

Please consult Consolidated Sterilizer Systems if you have any questions or concerns about vivarium sterilization.

 

[1] See The Guide for the Care and Use of Laboratory Animals housing space requirements for mice in groups.

Table 2

Table 2

 

The Center for Disease Control created ABSL to establish standards for quality, safety, and care in the laboratory.  The table below provides a summary of the containment levels, autoclave design requirements, and cage processing procedures.

 

Table 1

Table 1

17 Questions to Ask Before Buying Your Next Autoclave

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