Which safety precaution is necessary before conducting a blower door test?

Which safety precaution is necessary before conducting a blower door test includes several critical steps to protect occupants, equipment, and building. First, ensure combustion appliances are off or in safe mode, because blower door depressurizes house to minus 50 pascals which can cause backdrafting of furnaces, water heaters, and fireplaces that can spill carbon monoxide into home, so turn off atmospheric combustion appliances, ensure power vents are operating, or perform worst-case combustion safety testing before and after. Second, ensure occupants, especially elderly and infants, are aware test will cause drafts and pressure changes. Third, secure loose items that could be blown around, close interior doors to prevent slamming, and cover ashes in fireplaces. Fourth, check for lead paint and asbestos, do not create dust that could be hazardous. Fifth, ensure blower door is properly installed so it does not fall out. Sixth, avoid testing in high winds or extreme temperatures that affect accuracy and comfort. Seventh, ensure no one is using exhaust fans that interfere. Most importantly, never leave blower door unattended while running, monitor for signs of backdrafting with carbon monoxide detector, and after test, return all combustion appliances to normal operation and verify they vent properly.