Final answer:
OSHA regulations dictate that a paint spray booth must have sufficient dilution air to reduce flammable material vapor to 25% or less of the lower explosive limit for safety.
Step-by-step explanation:
A paint spray booth operation, according to OSHA, should provide enough dilution air to reduce the vapor of flammable materials to 25% of the lower explosive limit. This is to ensure that the concentration of flammable vapors remains well below a level that could cause an explosion or fire if an ignition source is present. Maintaining a vapor concentration below 25% of the lower explosive limit is a critical safety measure in any environment where flammable materials are used or stored.