The auxiliary power unit （APU） system for civil aircraft is installed in the APU compartment at the rear fuselage of the aircraft. During the initial 5 minutes of a fire in the APU compartment, assuming a delay in fire detection, manual or automatic shutdown, and discharge of fire extinguishing agent, the APU system may continue to operate. During this time, combustible smoke and toxic gases from non-metallic materials inside the APU compartment and APU air intake system can easily enter the cockpit and cabin, posing a significant safety risk to personnel. In response to airworthiness verification requirements, research into the smoke and toxicity testing standards for APU air intake systems was conducted. A study was carried out on the APU air intake system smoke and toxicity airworthiness compliance test for a certain type of civil aircraft. The result shows that the APU intake system of this type of civil aircraft will not cause smoke toxicity to cause gas pollution.