Convection Oven: Regulatory Requirements | Paint & Coatings Resource Center

EPA Self-Audit and Inspection Guide
Organic Finishing of Metals

Convection Oven: Regulatory Requirements

Air
The Clean Air Act regulates the emission of volatile organic compounds (VOCs) (40 CFR Part 60) and hazardous air pollutants (HAPs) (40 CFR Part 61 and 40 CFR Part 63), and provides specific standards of performance to control emissions from various types of coating operations (40 CFR Part 60). Depending on the solvent content of the coating material applied, sufficient VOC and HAP emissions could develop in convection ovens to subject an operator to major source requirements and Title V permitting requirements. The Act also regulates the formation of nitrogen oxides (NOx) from combustion sources; however, emissions of NOx are often well below compliance levels for small operations.

Controlling VOC emissions can be accomplished in two ways. A coating material with a lower VOC content can be used. Otherwise, air pollution control equipment is required on curing oven exhaust systems to recover or incinerate the VOCs and HAPs before they are released from the facility. Controlling NOx emissions can be achieved by adding oxidation systems, scrubbers or adsorbers to the exhaust system if necessary.

Self-Audit/Inspection

Do exhaust air streams have air pollution control equipment attached? Is that air pollution control equipment working properly? Does the final exhaust air have concentrations of pollutants below required levels?

Convection Oven: Common Causes of Violation

Emission of volatile organic compounds or hazardous air pollutants from convection oven structures may occur and exceed limits allowed by Clean Air Act Title V permits. The quantity of VOCs or HAPs released from the curing coating material depends on the amount of organic solvent in the coating formulation. These emissions in the exhaust air stream can be captured and treated to prevent their release to the atmosphere. Common air pollution control tactics include solvent recovery, solvent incineration, and solvent concentration.

Emission of nitrogen oxides (NOx) may occur and exceed limits allowed by Title V permits. The quantity of NOx formed depends on the amount of combustion products and evaporated diluent that combine and come in contact with a direct flame.

Convection Oven: Sources of Pollution Emissions of nitrogen oxides (NOx), when products of combustion and curing contact a direct flame (dependent on the coating material formulation). Heat loss through oven doors, heated work pieces, poorly insulated walls, and improperly sealed panels. Emissions of volatile organic compounds and hazardous air pollutants (dependent on the coating material formulation). Parts which have been improperly cured (overcured or undercured), resulting in the need to strip and recoat.

Convection Oven: Pollution Prevention Alternatives

Nitrogen oxide (NOx) emissions can be reduced by introducing fresh air into the combustion chamber. Fresh air will lower the flame temperature and prevent NOx formation. Heat loss can be reduced by improving insulation of the structure, and sealing panel joints. Proper curing can be achieved consistently by monitoring air flow circulation systems for accurate operation. Volatile organic compound and hazardous air pollutant emissions can be reduced by using powder coating or waterborne coating formulations, rather than solvent-based coating materials.