As you know the AVMA has recently updated its Guidelines for the Euthanasia of Animals.  In particular, the recommended displacement rate for Carbon Dioxide (CO2) euthanasia has been changed from [10% – 30%] to [30% – 70%].  The actions required to configure your Euthanex equipment to be compliant with the new guidelines varies greatly depending on the type of equipment you are using and the desired gas flow rate.  Answers to the most common questions can be found below.


E-Z Systems Solutions for Higher Flow Rate Compliance

30200-A1-MA3 High Volume Flow Meter

Designed for retrofitting existing SMARTBOX Chambers to comply with New AVMA Guidelines.


880 High LPM Flow Meter

Choose from three mounting options on this adjustable Flow Meter


EP-218 Low Flow CO2 Regulator

2 – 18 LPM Output – Incorporates an adjustable flow meter


Will higher flowrates cause my CO2 cylinder to freeze?

When operating at higher flow rates this causes a rapid lowering of temperature of the remaining liquid. As a result, the extreme cold causes the liquid to solidify into a snow-like consistency. This can be in the form of frost that accumulates on the internal components of the regulator and eventually causes complete blockage and loss of flow. Heat can relieve or eliminate freeze-up problems, we recommend heat be utilized on flow rates higher than 12 lpm or if the CO2 is used in continuous operation. Flow rates above 65 lpm will require a minimum of two CO2 cylinders ganged together and run through an independent heater system.

E-Z Systems Solutions for preventing Tank Freeze Ups

E-2200-H Heated Dual Regulator

For use with cage level systems


EA-6500 Multi Tank Heater Assembly

For use with SmartBox and multi-tank setups


We have one or more Euthanex SmartBox chamber systems, what do we need to do?

This depends on the model of SmartBox you have at your facility.  Some models will not require any modification to comply, others will require some modification and/or a new gas supply system.  A document is available upon request with a list of all SmartBox chamber models and what is required for compliance with the new guidelines for each.  Please contact us to obtain a copy.


We have a SmartBox chamber system that requires modification, how do we get this done?

In most cases any modification of your SmartBox will either need to be performed by a factory authorized technician on-site or the controller shipped back to E-Z Systems. Rarely will you be able to perform the modification yourselves. E-Z Systems will be implementing an exchange program for SmartBox electronic controllers to make this process as simple as possible. If your system requires a new gas supply system, we can provide instructions for installation or a technician can visit to perform the installation. A document is available upon request with a list of all SmartBox chamber models and what is required for compliance with the new guidelines for each.  Please contact us to obtain a copy.


We have a SmartBox chamber system and would like to operate at the highest possible displacement rate.  What is the maximum flow we can get out of our system?

E-Z Systems/Euthanex highly recommends that our chamber systems are operated at the lower end of the allowed range, 30% – 40%.  Due to physical limitations when working with CO2 gas, operating your chambers at higher flow rates can be impractical, inefficient, expensive and in many cases, unsafe.  Through years of in-house testing and anecdotal evidence from users, we have determined that a 30% displacement rate is ideal in terms of animal welfare as well as operator safety and efficiency.  Feel free to contact us with any specific questions on this stance.


We are using Euthanex Lids, either with a SmartBox controller or with a Regulator/Flowmeter, what do we need to do?

E-Z Systems provides three methods for controlling flow rate to a Euthanex Lid: Flow meters, Flow Restrictors or the SmartBox Prodigy device.  Flow meters will have a “ball-in-tube” configuration where flow rate (liters per minute/LPM) is controlled by a knob or screw.  They may be mounted on a tank regulator or operated as a separate device. Flow restrictors are a brass fitting installed in the top of the Euthanex Lid that operates at a fixed flow rate based on the incoming pressure.  The SmartBox Prodigy is an electronic touchscreen controller that delivers gas to the Euthanex Lids.

When using a flow meter, you may simply set the flow meter to the new desired rate.  To determine the flow rate, take the dimensions of your cage or chamber and perform the following calculation:

L x W x H (cm) = Volume in cubic centimeters (cm3)

cm3/ 1000 = Volume in Liters (L)

L x [30% – 70%] = Flow Rate in Liters per Minute (LPM)

If you are using Flow Restrictors, these have already been configured to deliver a 30% displacement rate and thus are already in compliance with the new guidelines.  If a higher displacement rate is desired, new flow restrictors will need to be installed in the Euthanex Lids.  In this case, please contact E-Z Systems with the dimensions of your cages and the desired displacement rate.  We will then contact you with the cost of new restrictors and instructions for their installation.

If you are using the SmartBox Prodigy, consult the operator manual for details on setting flow rate.


I hope that you find this information helpful.  Please direct any questions or concerns to your E-Z Systems associate or representative. Or contact us by calling 877-559-0159 or by using our form here.