The Essentials of Ventilation
by Mike Aurelius
Throughout this article, the issues discussed will adhere as closely as possible to any existing United States codes, be it building codes, mechanical codes, electrical codes, recommended practice, and other considerations. Occasionally, a method will be pointed out as being outside the codes, and if your studio utilizes a method like that described, you would be well advised to change your method to follow the codes. What will be discussed in this article will not be cheap or inexpensive. Doing it right is expensive, yet affordable. Many times, our inspiration for creation overrides good sense of health and safety. We all know that ventilation is important and that we need appropriate ventilation. There are several questions we should ask ourselves. What is appropriate ventilation, for example, and what makes one design good and another one inefficient and unsafe? It is my hope that this article will inspire you to consider your health, starting with good ventilation.
Coming to Terms with the Terms Okay. It’s definition time.
Ventilation is:
1. the act or process of ventilating
2a. circulation of air (as in a room with good ventilation;
2b. the circulation and exchange of gases in the lungs or gills that is basic to respiration
3. a system or means of providing fresh air
Definition number three is the important one for consideration here—a system or means of providing fresh air. The gas/air or gas/oxy torches we use produce combustion by-products such as carbon monoxide and nitrous oxides, also called NOX. When the glass we use is heated to melting, rare earth and metal vapors are also added to the foul mix. All of these nasty contaminates must be exhausted from the room, preferably outside to an area where they can be diluted with fresh air and dissipate. The chief “bad actors” are the nitrogen oxides, especially nitrogen dioxide, that are produced by any high-temperature flame. In addition to producing the familiar “torch smell,” nitrogen dioxide is a severe respiratory irritant with a very low acceptable air concentration.
Consider this: The flames we use range from reduction to oxidizing. The presence of excess amounts of oxygen greatly reduces the possibility of carbon monoxide, therefore reducing the risk. You should be concerned about carbon monoxide when you are using a highly reducing or sooty flame. Dilution Versus Local Exhaust Ventilation There are two types of ventilation systems, dilution and local exhaust ventilation. Dilution ventilation uses large amounts of fresh air to dilute contaminated air in the workplace. The diluted air is then exhausted from the studio. It is paramount that your “makeup” or fresh air source is not in the proximity of your exhaust. This promotes the recycling of contaminated air in your shop or studio. While the most widely used system might be an attic fan and an open door, it is far from the most effi cient. This is especially true if you are heating or cooling your shop because of the high air fl ow requirements. Dilution ventilation should only be used to control small amounts of toxic vapors and should not be used to control dust or powder contaminants. The ventilation systems discussed here are local exhaust. A local exhaust ventilation system consists of four components: a method of gathering and concentrating the fumes, a device for pulling and/or
