With the new 2013 edition of the AVMA Guidelines on Euthanasia, a flow meter is now required for all CO2 tanks used for euthanasia. A flow meter measures the rate of gas passing through the nozzle (volume per unit of time). In combination with the regulator, which tells you the psi left in your tank, flow meters allow for precise and accurate delivery of CO2. Flow meters can be purchased from several vendors including Praxair. Contact your Compliance Advisor for more information.