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The National Fire Protection Association (NFPA) requires specially designed "Class A" ovens for direct, gas-fired equipment, or for processing products involving flammable solvents, volatiles or combustible materials. A Class A oven must have a forced exhaust, a method to prove airflow, a purge timer and an explosion relief area. Despatch Class A ovens are specifically designed to meet NFPA 86 requirements. A Despatch Class A oven comes complete with a pressure relief panel, purge timer, and exhaust fan.

Do you need a Class A oven?

If you process a flammable product or remove combustible vapors from a product in an industrial oven, you will need a Class A oven that meets NFPA 86 requirements. Flammable volatiles that pose a potential explosion or fire hazard can originate from paints, powders, inks, and adhesives. Potential threats may also originate from finishing processes, such as dipped, coated, sprayed, and impregnated materials as well as from polymerization or other molecular rearrangements. Combustible materials include substrate material, wood, paper, plastic pallets, spacers and packaging materials.

Inadequate training of operators, lack of proper maintenance, and improper application of equipment can cause serious injury. For the latest safeguards required to minimize explosion hazards, get a copy of NFPA 86 Standard for Ovens and Furnaces, 2019 Edition, from the National Fire Protection Association (www.nfpa.org).

Better safe than sorry

If you have multiple ovens and any one of them is used for processing combustible products, it is recommended that all be Class A. This will prevent someone accidentally using the wrong oven which could result in a catastrophic incident.

Many of the NFPA guidelines and specifications are temperature dependent due to the rate of evolution so it is important that a Class A rated oven never be loaded hot.

Despatch incorporates all pertinent NFPA required safety testing, visual inspection and required documentation in all Preventative Maintenance and Calibration Service Agreements.

NFPA 86 has requirements for annual inspection, operational testing, documentation of testing, and visual inspection of certain oven components such as:

  1. Safety interlocks
  2. Set point of temperature, pressure, and flow devices used as safety interlocks.
  3. Pressure and explosion relief panels.
  4. Gas heater components.

Contact your Despatch Sales Representative for more information.

Despatch recommends the use of an airflow switch with the forced exhaust to prove airflow.The forced exhaust is sized to keep the flammable solvent vapor concentrations below the lower explosive limit (LEL) in the oven chamber. The purge timer operates in conjunction with the forced exhaust to purge the oven of volatiles before the heaters are allowed to energize.The purge time is based upon the volume of the oven, as the oven air must be changed four times before the heater may be energized. The airflow switch is used to prove exhaust airflow. With no airflow, the heating system shuts down via the airflow switch. The explosion relief area is typically incorporated into the oven by means of an explosion relief panel/door or explosion relief membrane.

RFD Class A Oven

Like all Despatch Class A ovens, the RFD1-42 Class A Benchtop oven features a pressure relief panel, purge timer and exhaust fan.