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Ventilation and natural gas/air torch

Hi folks, We have discussed this matter before, but I still have
questions about it. I am setting up a small studio space in the
basement of my house in New Jersey. The size is about 360 square
feet. I understand that the natural household gas lines have enough
pressure to feed a jewelry torch, but would it be enough for the #2N
silversmith’s torch (in combination with compressed air)? Also, I am
planning to use a 600 CFM squirrel cage blower over an enclosed hood.
The length of the ducts is about 4 feet, including two 90 degree
elbows, and the diameter is 6". Would that be enough to exhaust fumes
generated by soldering small hollow ware pieces, annealing metal and
melting chaser’s pitch? Thanks in advance! Valentin Yotkov

Valentin, Do you have a daylight basement with windows or door looking
out on one side ? It is my understanding that, in a basement that is
an enclosed space surrounded by dirt on all four sides, the gas will
tend to pool in the room if you have a leak and that local authorities
would not approve the plan for fire safety. Sincerely, Rose Alene

Hi Valentin,

Assuming the blower is connected directly to the hood that should
remove all the fumes generated from soldering & annealing.

However all the air that is removed by the blower must be replaced by
air from someplace. Typically the furnace, water heater and laundry
equipment are installed in many basements. If these devices are fired
by natural gas, propane or oil, they generate exhaust gases, one of
which is carbon monoxide. The exhaust gases are generally vented
through a chimney. There are no check valves (reverse flow preventers)
in chimneys.

The 600 cfm removed by the blower must be replaced with air from
somewhere. The easiest way for air to get into a relatively sealed
basement is via the chimney or any other outside vent. This will cause
the exhaust gases to reverse their flow & fill the basement until
they’re expelled by the 600 cfm blower.

In addition, the force of the air coming down the chimney may blow
out pilot lights in gas operated equipment. If there are any
improperly operating valves in the equipment, this could result in gas
collecting in the basement & an explosion when conditions are right.

One way to avoid the back drafts when the exhaust blower is on is to
put the soldering/annealing hood in a room by itself. Then provide a
separate fresh air intake to that room. If the fresh air intake is
gravity fed ( no fan) the opening should be about twice the size of
the blower outlet. A barometric damper could be added to the fresh air
intake to close it off when the blower isn’t operating.


Valentine, I’ve heard you’re a wonderful teacher! I thought you
taught classes in NY, but I live in NJ. Will you be teaching in
Jersey? If so, I’d love more You can e-mail me at
@Dawn_Hale or post a message on orchid. Thanks!