Gas Fitter Practice Test

Where are air filtration devices generally located?

1. Supply air plenum

2. Fresh air plenum

3. Return air plenum

4. Exhaust air plenum

The correct answer is: Return air plenum

Air filtration devices are typically located in the return air plenum because this is the area where indoor air is drawn back into the heating, ventilation, and air conditioning (HVAC) system. By positioning the filters here, contaminants and particulates can be removed from the air before it is re-circulated and conditioned. This placement helps to improve indoor air quality and ensures that cleaner air is supplied to the living spaces, contributing to a healthier environment. The return air plenum acts as the main conduit for air that has already circulated through the occupied spaces, thus making it the ideal location to capture dust, allergens, and other pollutants present in the indoor air. Proper filtration at this point also protects HVAC equipment from dirt and debris buildup, which can lead to inefficiencies or damage over time. While air filtration devices could conceivably be placed in other locations such as the supply air plenum or fresh air plenum, doing so would not effectively address the quality of the air being reintroduced into the system and could allow for unfiltered air to circulate. The exhaust air plenum is focused on expelling air outside and is not suitable for filtration purposes. Therefore, locating air filtration devices in the return air plenum optimizes air quality and system performance