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  • Understanding AVMAGuidelines
  • Calculating AVMA Compliant Flow Rates
  • Auto vs Manual

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Auto CO2 vs. Manual



Manual euthanasia technique requires a trained technician to introduce CO2at specified flow rates. The American Veterinary Medical Association (AVMA) 2013 Guidelines on Euthanasia recommend a displacement rate of 10% to 30% total volume of the cage or chamber size. Basing the fill rate at the 30%, it will take about 3:30 minutes of charge time to euthanize a standard mouse cage (7"Wx 11"D x 5"H). Rats will require longer exposure times with approximately 6 minutes per standard rat cage (10"W x 19"D x 8"H). Most facilities will also require a set exposure time after the initial charge to ensure the animals are dead. This time can be as little as 3 minutes or up to an hour, depending on species, size, and age.

For the purpose of this illustration, the flow rate is calculated at a displacement rate of 30% of cage volume for a standard mouse cage. This equates to a charge time of 3:30 minutes with an additional dwell period of 3 minutes. A single mouse cage with up to 5 mice can be properly euthanized in 6.5 minutes. Based on the flow rate of 30%, a charge time for 6 minutes, and an additional dwell period of 3 minutes, a single rat cage containing 2 to 3 rats can be properly euthanized in 9 minutes. Since it is difficult to put an average on the additional time required for a secondary method, this comparison assumes no secondary method is needed. Secondary kill methods can be avoided by using proper equipment, correct flow rates, adequate exposure time, trained personnel, and adhering to established SOPs.

Automated SMARTBOX M1-SBFF Single Chamber System:

The M1-SBFF can accommodate up to 20 standard shoe box mouse cages. The total cycle time is 17 minutes for adult mice. The system has an automatic three stage sequence. The first stage is the CO2 Charge of 8:30 minutes at a 25% displacement rate. Animals are gently anesthetized as the CO2 level builds and continues rise until animals are euthanized. This stage is followed by a standard 5 minute Dwell period for adults or a longer period depending on the species, size, or age. The Dwell stage provides sufficient exposure time for the animals to the high concentration of CO2 to ensure proper euthanasia – eliminating the need for secondary kill methods. The final stage is 3:30 minute Exhaust period. During the Exhaust stage, the CO2gas inside the chamber is evacuated and replaced with outside ambient air.

Comparison of Manual vs. Automated CO2:

In 17 minutes a manual process will produce 2.5 mouse cages. It will take a technician 2 hours and 10 minutes to euthanize 20 standard mouse cages that a single SMARTBOX cycle performs in less than 20 minutes. This does not take into account that the SMARTBOX can be loaded, started, and allows the technician to perform other duties during the cycle. A base rate of a technician is $20 an hour that equals a cost of $43 to euthanize 20 cages. That is a cost of $2.15 per cage for the technician’s time. An efficient, single technician can only perform 9 cages an hour, 72 cages a day assuming an 8 hour day without taking any breaks at a cost of $160 per day.

SMARTBOX offers an entire line of automated euthanasia systems to accommodate your facility’s and technicians’ daily needs. Using standard shoe box cages for adult mice:

  • M1-SBFF-1FM Single Chamber System = 20 cages at 17 minutes per cycle. That is approximately 60 cages an hour.
  • M1-SBFF-2FM Double Chamber System = 40 cages at 21:30 minutes per cycle. That is approximately 120 cages an hour.
  • MSVF-4 Four Chamber System = 80 cages at 20 minutes per cycle. That is approximately 240 cages an hour.
  • MSVF-8 Eight Chamber System = 160 cages at 23 minutes per cycle. That is approximately 480 cages an hour.


The SMARTBOX pays for itself in a short amount of time. Beyond cost savings, the SMARTBOX equipment has built-in safety measures to protect personnel. SMARTBOX also ensures the euthanasia cycles are consistent to the AVMA Guidelines every time and virtually eliminates human error, uneasiness, and stress. For medium to large facilities, the return on investment for the cost of a SMARTBOX is unquestionably a smart management decision.