Firing ceramics produces fumes that contain small amounts of carbon monoxide, formaldehyde, and sulfur dioxide. Fiber paper, which is sometimes used as a glass separator, also produces fumes.
For health reasons, we recommend—and building codes in some areas require—that kilns are vented with a motorized vent.
The two vent systems available for electric kilns are the overhead system made by Vent-A-Kiln Corporation, and the down-draft system made by Orton Ceramic Foundation. To help you plan your kiln location, we are including basic information on these systems. For further information, contact the vent manufacturers or your ceramic supplier:
Orton Ceramic Foundation 614-895-2663 / Fax 614-895-5610 www.ortonceramic.com
Vent-A-Kiln Corporation 716-876-2023 / Fax 716-876-4383 www.ventakiln.com
Vent System Operation Theory
The overhead vent is positioned over the kiln with the aid of a counter-weight. As heated air rises from the kiln, the vent pulls it outside through an aluminum duct. This system also helps lower room temperature around the kiln.
The down-draft vent connects directly to the kiln. For top-loading kilns, the vent fits between the kiln and the kiln stand. A small amount of air is pulled from the kiln and mixed with room air. This lowers the temperature of the vented air to a safe level. Small holes drilled in the kiln lid and bottom regulate the amount of air that the vent pulls from the kiln.
Vented Air Volume & Temperature
Both vent systems remove air from the kiln room. Open a window or door to replace the air that is vented outside. Many studios keep the door to the kiln room closed. In this case, you must open a window or install an intake vent so that make-up air can enter the kiln room. Volume of Vented Air Orton KilnVent 60 - 80 CFM Vent-A-Kiln 265 - 500 CFM
Approximate Duct Temperature Orton KilnVent 100°F - 155°F Vent-A-Kiln 90°F - 125°F
Installing the Vent
The Vent Exit Point
Plan your kiln room to include an exterior wall. The fumes are vented to the outside through a clothes dryer duct. If the kiln room does not have an exterior wall, you will need to run the duct through the ceiling or floor to the outside. Avoid placing the vent exit near windows. Otherwise the fumes may reenter the room. If you are in a multi-story building, avoid placing the vent exit under upper story windows.
If you cannot avoid placing the vent exit near a window, you can raise the vent above the level of the window. As the warm air is vented outside, it will rise past the window.
The Vent Duct
The duct size will depend on the type of vent you are installing. Several kilns can be vented to a single exit duct. The size of the exit duct depends upon the number of kilns vented and the brand of vent.
Duct Length and Width Maximum Length Width Orton KilnVent 60’ with 4 - 90° turns 4” Orton KilnVent 60’ with 8 - 45° turns 4” Vent-A-Kiln 10’ with 2 - 45° turns* 5” & 6” *20’ if you extend the duct with rigid duct.
It is okay to include vertical lengths of duct, because the warm air rises. Use aluminum flexible duct. Do not use the plastic flexible duct sometimes used on clothes dryers.
You can use 4” PVC pipe, provided your building code approves. PVC lasts longer than aluminum duct, especially if you fire clay with a high sulfur content.
Do not connect the PVC directly to the KilnVent. Instead, use several feet of flexible aluminum duct between the vent and the PVC. This prevents vibration of the motor from transferring to the PVC.
Seal all joints with duct tape. When aluminum duct begins to deteriorate, small holes will appear, and you will begin to smell kiln fumes. At that point, replace the duct rather than attempt to repair with duct tape.
If you fire the kiln with the Orton KilnVent turned off or removed for repair, cover the air exit holes in the kiln bottom. Place a kiln shelf over the holes.
Leave the vent on throughout the kiln firing and cooling cycle. Turn the vent off when the kiln is cool enough to unload bare-handed. The vent will help remove moisture during “candling” at the beginning of the firing. The moisture in the duct and motor will dry out as the kiln heats.
When using the Orton KilnVent, leave the kiln’s peephole plugs in place and lid down all the way throughout the firing. The vent operates under negative pressure, which requires that the lid and peepholes are closed.
With best wishes,
Arnold Howard Paragon Industries, L.P. - Better Designed Kilns 2011 South Town East Blvd. Mesquite, TX 75149-1122 Voice: 972-288-7557 & 800-876-4328 / Fax: 972-222-0646 firstname.lastname@example.org / www.paragonweb.com