Kiln Safety in Schools
Gas- and electric-fired kilns are commonly found in school art rooms, artisan shops and manufacturing facilities. As with other types of heat-producing equipment, there are risks of fire and personal injury associated with kiln operation. To reduce these risks, follow the guidelines outlined below.
Kiln Room Ventilation Requirements
The clay firing process produces carbon monoxide and various other combustion gases that may cause adverse health effects. Studies show that carbon monoxide levels around operating kilns are in excess of 400 ppm, well above the OSHA standard.
Additionally, certain clays, glazes and fuels also produce gases (e.g., chlorine, fluorocarbons, sulfur dioxide, nitrogen oxides and ozone) that may be released during the firing process.
For these reasons, it is essential to provide adequate ventilation. At a minimum, kilns should be equipped with a ventilation hood, ductwork and an exhaust fan that removes gases and harmful byproducts of the firing process.
The ventilation system should be designed and installed by a qualified contractor, balanced to handle the maximum amount of air flow and vented directly to the outside environment.
A downdraft ventilation system is the best option for ventilation. This method removes combustion gases prior to them entering the surrounding room. Canopy hoods can also be used; however, their effectiveness depends on the distance of the hood above the kiln and the amount of makeup air coming into the room. To be efficient, the hood must be 12 to 30 inches above the kiln and at least 250 cubic feet per minute (cfm) of makeup air must be delivered into the room.
When using natural gas or propane-fired kilns, install carbon monoxide alarms. If excess carbon monoxide is detected, move all individuals out of the room, shut the gas off at the source and power down the kiln. High carbon monoxide levels are usually caused by an improperly designed or poorly operating ventilation system—get them repaired by a qualified contractor or ventilation professional.
Clearances for Kilns
Locate kilns at least 18 inches from noncombustible surfaces and 36 inches from combustible surfaces. And always place kilns on noncombustible flooring (i.e., solid masonry or concrete that is 2 inches thick), extending 12 inches beyond the base of the kiln.
When determining clearances, remember to allow adequate room for opening, loading and routine maintenance tasks around the kiln. Be sure to read and follow manufacturer's recommendations regarding kiln placement.
Preventing Kiln Fires
To avoid kiln fires, keep combustible materials at least 36 inches from the kiln during operation. Items such as paper, solvents and flammable liquids should be kept at an even greater distance.
A multipurpose A-B-C dry chemical fire extinguisher should be kept near the kiln. And make sure those using the kiln are trained annually on the proper use of the extinguisher.
Electrical Kiln Guidelines
Before installing an electric kiln, make sure the correct voltage, amperage and phase are available. Employ a licensed electrician to install the proper electrical supply. Kilns must be properly grounded and installed in accordance with all national and local electrical and fire codes.
Do not use an electric kiln in wet conditions and always unplug all equipment when conducting any type of servicing or maintenance.
Personal Protective Equipment When Using a Kiln
Personal protective equipment (PPE) must be used at all times when working with a kiln. Heat-resistant gloves should be used for removing peepholes and when unloading fired items. Shade #3 welding glasses should be used when looking into an operating kiln.
These glasses offer protection against infrared radiation, which is hazardous to the eyes and can cause cataracts after years of exposure. Everyone working with kilns must be trained to use proper PPE and usage should be enforced at all times.
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