Hazardous Location Classification for a Paint Booth
A paint booth uses a solvent with a flash point of 100°F and a boiling point of 300°F. The booth is a closed-top, open-face design with a 4 ft opening. The ventilation system is mechanical and interlocked with the spray equipment. The area within 5 ft of the open face is considered Class I, Division 1. The area beyond 5 ft up to 10 ft is Class I, Division 2. The electrician installed a general-purpose junction box inside the booth, 3 ft from the open face, and a standard light fixture 8 ft from the open face. The wiring method is EMT with compression fittings. The AHJ requires compliance with NEC Article 516. The booth is in a building with other operations.
1. Evaluate the classification and the installed equipment for compliance with NEC Article 516.
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The solvent has a flash point of 100°F, which is below 100°F? Actually, 100°F is the threshold for Class I liquids? NEC defines flammable liquids as having a flash point below 100°F, and combustible liquids at or above 100°F. So this solvent is a combustible liquid, not flammable. Therefore, it may not require Class I classification. However, Article 516 covers spray application using flammable or combustible materials. For combustible liquids, the classification may be different. But the problem states the area within 5 ft is Class I, Division 1, and beyond 5 ft to 10 ft is Division 2. That classification is typical for flammable liquids. But with a flash point of 100°F, it might be Class II or III? Actually, NEC 516.5 classifies areas based on the liquid. For a liquid with flash point at or above 100°F, it is a combustible liquid, and the area classification may be Class I, Division 2 or unclassified? However, the problem states the AHJ has already determined the classification as Div 1 and Div 2. So we accept that. Now, the junction box 3 ft from the open face is in the Div 1 area. General-purpose junction boxes are not permitted in Div 1; they must be explosionproof or intrinsically safe (NEC 501.10). So the junction box is noncompliant. The light fixture 8 ft from the open face is in the Div 2 area. Standard light fixtures are not permitted in Div 2 unless they are suitable for the location (NEC 501.10(B)). So the light fixture is also noncompliant. The EMT with compression fittings is not permitted in Div 1 or Div 2? In Div 1, threaded rigid metal conduit is required (501.10(A)). In Div 2, EMT with compression fittings may be permitted if listed for the location? Actually, 501.10(B) allows EMT with compression fittings in Div 2 if it is listed for the purpose? But generally, EMT is not permitted in hazardous locations unless specifically listed. So the wiring method is likely noncompliant. Therefore, the installation is noncompliant and must be revised.
2. What changes would you recommend to bring the installation into compliance?
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For the junction box in the Div 1 area, replace it with an explosionproof junction box listed for Class I, Division 1. For the light fixture in the Div 2 area, replace it with a fixture listed for Class I, Division 2. For the wiring method, in Div 1, use threaded rigid metal conduit with explosionproof fittings. In Div 2, use threaded rigid metal conduit or EMT with listed compression fittings if permitted, but best to use rigid. Also, ensure all seals are installed per NEC 501.15. Additionally, verify the area classification: if the solvent is a combustible liquid (flash point 100°F), the classification may be less severe, but since the AHJ has determined Div 1 and Div 2, we must comply. So recommend upgrading equipment and wiring methods to meet the classification.