Mechanical ventilation shall be kept in operation at all times while spraying operations are being conducted and for a sufficient time thereafter to allow vapors from drying coated articles and finishing material residue to be exhausted. Spraying equipment shall be interlocked with the ventilation of the spraying area such that spraying operations cannot be conducted unless the ventilation system is in operation.
Air exhausted from spraying operations shall not be recirculated.
- Air exhausted from spraying operations shall be permitted to be recirculated as makeup air for unmanned spray operations provided that:
- Solid particulate has been removed.
- The vapor concentration is less than 25 percent of the lower flammable limit (LFL).
- Approved equipment is used to monitor the vapor concentration.
- An alarm is sounded and spray operations are automatically shut down if the vapor concentration exceeds 25 percent of the LFL.
- The spray booths, spray spaces or spray rooms involved in any recirculation process shall be provided with mechanical ventilation that shall automatically exhaust 100 percent of the required air volume in the event of shutdown by approved equipment used to monitor vapor concentrations.
- Air exhausted from spraying operations shall be permitted to be recirculated as makeup air to manned spraying operations if all of the conditions provided in Exception 1 are included in the installation and documents have been prepared to show that the installation does not present life safety hazards to personnel inside the spray booth, spray space or spray room.
Ventilation systems shall be designed, installed and maintained such that the average air velocity over the open face of the booth, or booth cross section in the direction of airflow during spraying operations, is not less than 100 feet per minute (0.51 m/s).
Articles being sprayed shall be positioned in a manner that does not obstruct collection of overspray.
Each spray booth and spray room shall have an independent exhaust duct system discharging to the outdoors.
- Multiple spray booths having a combined frontal area of 18 square feet (1.67m2) or less are allowed to have a common exhaust where identical spray-finishing material is used in each booth. If more than one fan serves one booth, such fans shall be interconnected so that all fans operate simultaneously.
- Where treatment of exhaust is necessary for air pollution control or energy conservation, ducts shall be allowed to be manifolded if all of the following conditions are met:
- The sprayed materials used are compatible and will not react or cause ignition of the residue in the ducts.
- Nitrocellulose-based finishing material shall not be used.
- A filtering system shall be provided to reduce the amount of overspray carried into the duct manifold.
- Automatic sprinkler protection shall be provided at the junction of each booth exhaust with the manifold, in addition to the protection required by this chapter.
The termination point for exhaust ducts discharging to the atmosphere shall be located with the following minimum distances.
- For ducts conveying explosive or flammable vapors, fumes or dusts: 30 feet (9144 mm) from the property line; 10 feet (3048 mm) from openings into the building; 6 feet (1829 mm) from exterior walls and roofs; 30 feet (9144 mm) from combustible walls and openings into the building which are in the direction of the exhaust discharge; 10 feet (3048 mm) above adjoining grade.
- For other product-conveying outlets: 10 feet (3048 mm) from the property line; 3 feet (914 mm) from exterior walls and roofs; 10 feet (3048 mm) from openings into the building; 10 feet (3048 mm) above adjoining grade.
- For environmental air duct exhaust: 3 feet (914 mm) from the property line; 3 feet (914 mm) from openings into the building.
Electric motors driving exhaust fans shall not be placed inside booths or ducts. Fan rotating elements shall be nonferrous or nonsparking or the casing shall consist of, or be lined with, such material. Belts shall not enter the duct or booth unless the belt and pulley within the duct are tightly enclosed.