In automobile refinishing spray booths where drying by heat occurs inside the same spray booth, fire codes require interlocks to prevent ignition hazards.
Before activating the drying apparatus, the ventilation system must purge the booth of spray vapors for at least 5 minutes to remove flammable concentrations.
Reference to Fire Inspector Documentation:
1. 2021 International Fire Code (IFC) – Section 2404.7.3 (Drying Operations in Spray Booths)
IFC 2404.7.3 mandates that spray booths must have interlocks to purge vapors for a minimum of 5 minutes before activating the drying process.
This ensures that flammable vapors are removed before heat sources operate, reducing fire risks.
2. NFPA 33 – Standard for Spray Application Using Flammable or Combustible Materials (2021 Edition) – Section 15.4.6
NFPA 33, Section 15.4.6 confirms the requirement for a 5-minute ventilation purge cycle before heat drying.
Detailed Explanation of Answer Choices:
Option A (Incorrect): 2 minutes is insufficient for adequate vapor removal.
Option B (Incorrect): 3 minutes does not meet the minimum safety requirement.
Option C (Incorrect): 4 minutes is slightly below the code-mandated requirement.
Option D (Correct): 5 minutes is the minimum required purge time per IFC 2404.7.3 and NFPA 33.
Thus, the correct and verified answer is: D. 5.
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