Geoffrey and Barbara Proust explain their method of removing toxic lead fumes safely from their workshop when joint-soldering stained glass pieces.
My wife, Barbara, and I operate a stained-glass business out of our home studio . . . and although we both enjoy combining the independence of self-employment with the creativity of artistic endeavor, our craft does present us with a special problem.
Working with stained glass, you see, exposes us to toxic lead vapors given off in the joint-soldering process, as well as fumes from flux. Lead is an especially nocuous poison because it accumulates in the body with each exposure and can eventually result in anemia, kidney dysfunction, and even permanent brain damage.
Clearly, a solution was required when removing toxic lead fumes safely. It was obvious that simply forcing air across the workbench and into another part of the studio wasn't the answer, nor was relying upon a household window fan to do a major ventilation job. But the variable-position exhaust system I made (using a swing-arm incandescent desk lamp, a plastic bucket, some ducting, and a blower) provides positive suction and removal of the offending vapors at any point within a 6'-diameter circle on our table . . . at a cost (less than $45) that even a hobbyist could justify.
The system I devised consists of two components: the suction apparatus and the movable support arm for the suction head. The latter is just a swiveling all-position arm lamp of the kind frequently used for drafting and design work. To convert it, I drilled out the rivets that held the shade to its mount, removed the electrical parts (by clipping the plug and drawing the wire through the arms), and fastened a 7 inch-diameter plastic ice cream bucket in place of the shade, using No. 6 by 1/2 inch machine screws. A 4 inch opening cut into the bottom of the bucket accommodates the flexible suction tube.
The air-handling apparatus is almost as straightforward. Once I'd established where I wanted to bolt my support arm (a table-edge mount allows a 180 degree sweep, while a centrally located base provides a full 360 degree reach), I hung enough 6 inch round galvanized ducting overhead to reach from the nearest outside wall to a point above the arm. Then I attached about 7 feet of 4 inch flexible clothes-dryer hose to the hole in the plastic suction head and used a 4 inch-to-6 inch adapter to connect the hose's opposite end to the duct.
My exhaust fan is a used 2.9-amp squirrel cage blower with a free-air delivery rate of 350 cubic feet per minute (Dayton No. 2C841). Centrifugal fans are usually designed to blow, rather than draw, air, but I installed a 6 inch-duct adapter plate to its inlet anyway. By using the oversized duct, keeping its length and the number of elbows in it to a minimum, and cracking open a window to allow vented air to be replaced, I figure I've made an acceptable compromise between efficiency and cost. (One particular fan that's made just for ducted systems—the Dayton 1C791—costs over $100.) To install it, I cut an opening in the exterior wall, mounted the blower, and used a wall cap on the outside to cover and protect the exhaust outlet.
Naturally, my ventilation system would work with fumes, vapors, smoke, or anything without sizable particulate matter in it. But if the substance you're venting is flammable, be certain that the fan you choose is a non-sparking "explosion-proof" type, even though it'll cost more; by the same token, dusty substances will demand a sealed motor with greater power.