Spray Booth Operation and Maintenance
What the exam expects
Booth questions test airflow, filtration, temperature, and safety. Understand downdraft vs. crossdraft, balanced pressure, and why booth balance affects both finish quality and contamination. Know filter stages: intake/pre-filter, ceiling diffusion media, and exhaust floor filter.
Core concepts
- Airflow: a properly balanced booth moves air top-to-bottom (downdraft) at a controlled velocity, carrying overspray away from the wet film and out through exhaust filters.
- Filtration: ceiling filters clean incoming air; floor/exhaust filters capture overspray. Loaded filters reduce airflow, causing slower flash, more overspray settling, and defects like trash or orange peel.
- Temperature and humidity: most products specify a booth temperature (commonly around 70–75°F / 21–24°C). High humidity slows solvent escape; low humidity increases static and dust attraction.
- Safety: booth must be running during spraying; no open flames; proper respirator (supplied air or appropriate cartridge); grounding of the vehicle and equipment.
- Maintenance: change filters on schedule or when differential pressure indicates loading; clean walls and floor to prevent dust.
Traps
Questions often imply you can spray with the booth off "for a small job" - wrong. Others confuse intake and exhaust filters, or suggest raising temperature to fix a run (heat speeds cure but doesn't fix application error).
Worked example
A painter notices more trash in the finish and slower flash times. Checking the booth reveals a loaded floor filter and reduced airflow. The fix is to replace filters and verify airflow, not to add more reducer.
Rule of thumb: if the booth isn't balanced and filtered, no gun technique will save the finish.