If chemical generation through the use of sodium formate and sulfuric acid is used, the generated carbon monoxide gas must have all irritating acid vapors filtered out by passing it through a ten percent solution of sodium hydroxide prior to its entry into the carbon monoxide chamber. The engine shall be operated only at idling speed with the richest fuel-air mixture the choke permits. Prior to entry into the chamber, the exhaust gas shall be first passed through an adequate water-gravel filtration process and subsequently through a cloth filtration process to remove irritants and carbon particles. The noise level from the engine shall not exceed 70 dBA when measured within the chamber. Animals shall be left in the chamber for a period of no less than fifteen minutes from the time the gas concentration throughout the chamber reaches five percent.
Every animal is placed in an individual container or compartment of the cabinet.
The 1.5 percent reduction in oxygen concentration is reached within 45-50 seconds after the beginning of the cycle of operation and the animals are left within the cabinet at that concentration not less than ten minutes. Every chamber must be thoroughly cleaned after the completion of each full cycle. No live animals shall be placed in the chamber with dead animals. All chambers shall be inspected quarterly by an independent qualified technician who is thoroughly knowledgeable with the operation and maintenance of the particular euthanasia chamber being used. The animal to be killed shall be less than eight weeks old.