Are there any health and safety issues?
Testing has shown that carbon monoxide produced during firing can be higher than accepted government (OSHA) standards. 35 PPM (0.0035%) for continual exposure or 200 PPM for short term exposure. Carbon monoxide can produce headaches, fatigue, sore throats and nausea. Fumes from kilns may also contain organics, volatile metals, fluorides and sulphur oxides, which should be removed from the work area.
What are some of the benefits of a downdraft vent?
Air brought into the kiln replaces carbon monoxide and adds oxygen needed for best fired results. Oxygen in the kiln reduces corrosion of metal heating elements and kiln sitter parts, increasing their life. A downdraft vent costs less than two cents per hour to operate. It requires 80% less makeup air than a hood above the kiln and saves up to $1.00 per day for heating or cooling makeup air as compared to a hood. Manual venting is eliminated - no more touching the hot kiln to lower the lid or replace peephole plugs. The kiln stays closed throughout the firing and cool down is quicker (4 - 10 hours less) without opening the lid. Downdraft venting is much more effective than a hood in removing fumes. It does not significantly increase firing time or affect the ability of the kiln to reach temperature. Most kiln manufacturers recommend and sell downdraft venting. It is easily installed with no overhead pulleys. <strong>Only downdraft venting improves firing conditions in the kiln, while removing fumes from the kiln and workroom!</strong>
What happens to air in the kiln?
The products we fire contain carbon and organics. These react with oxygen to form carbon monoxide early in the firing. During firing, the gases in the kiln expand — just like air in a hot air balloon. These gases are forced out through cracks and holes, making it difficult for new air to enter the kiln. A downdraft vent system pulls out the fumes, allowing fresh air to enter.
What is the recommended procedure for firing with a manual kiln?
1. Place the correct jr. cone in the kiln sitter and set the falling weight. 2. Set the timer to 30 minutes past the anticipated firing time. 3. Prop the lid if kiln is not equipped with a downdraft vent. 4. Turn switches to LOW. 5. Two hours later, turn switches to MEDIUM. 6. Two hours later, remove the prop with a gloved hand and turn the switches to HIGH. 7. The kiln will shut off automatically when the proper heatwork has been achieved.
What safety measures should be taken when firing?
Always be present during the end of the firing cycle and cool down period, to prevent over-firing. The kiln surface emits heat. Do not install near combustible surfaces or under a sprinkler head. Do not touch the surface while firing, wait until cooled to 130°F before opening lid and always wear heat-resistant glooves.
What's the difference between a downdraft vent and a hood?
A downdraft vent removes fumes and odors from the kiln while at the same time bringing in air to improve firing conditions in the kiln. A hood system does not vent the kiln. It simply removes fumes that have already entered the room. There are no firing benefits and only about 85% of the fumes are removed. Conditions in the kiln are not improved with hoods.
Why vent a kiln?
Fumes, odors and vapors are created when clay bodies and glazes are fired. It is important to clear them out of inhabited spaces for the comfort and safety of those around. Additionally, the venting process affects the firing results. A venting hood will dispel most of the fumes as they escape the kiln. Mechanical downdraft systems improve consistent heat distribution and circulation, as well as remove fumes before they can enter the room, or transfer color from one glaze to another inside the kiln.