Alma,
You’ve mostly got it right, though a bit overstated Re: the propane
danger. A light switch won’t generally do the trick, since the gas
will be usually at floor level, and most light switches don’t generate
a spark. And for what it’s worth, propane accidents are quite rare.
But they CAN, and now and then, DO happen, and then it’s not nice. As
you note, propane is a heavy gas. And dense. So it sinks to floor
level with a leak. I small leak isn’t a problem, since as with any
gas leak, it does dissipate. But it dissipates somewhat slower than
most fuel gases, and fumes/gas levels at the floor level can
accumulate more than at, say, nose level, where it’s more easily
noticed. Now, if there’s a leak where you’re working, never fear,
you’ll smell it at nose level long before it’s even remotely
dangerous. And in most rooms of a house, especially if there is air
conditioning or forced air heating, air circulation is enough to
prevent “pooling”. the dangerous situations come when propane manages
to leak into, usually, basement or crawl spaces. These often are not
ventilated as well, so the gas isn’t as easily dispersed or disturbed
by air currents. And what else do we have in basements? Right.
Furnaces, and water heaters. And if gas fired, these have pilot
lights. Where? At floor level. If propane levels can build up to an
ignitable concentration at the floor level, then these pilot lights
can set it off. Now, for most basements, it should be noted that this
is not a small amount of propane from a slow leak. It’s gonna take a
fairly substantial leak, for quite a while. Like leaving your torch
valves wide open, but forgetting to light it, then leaving the
workroom for an hour or two while you go tend the yard… Or maybe an
outright broken regulator or tank valve. But if that happens, then
your house becomes quite unlivable really dramatically. And the leaky
tank does not always even have to be in the basement itself. Many
houses, especially older ones, have cold air return vents in various
rooms, where cold air sinks back down to the basement, to be again
heated by the furnace. Such a floor level opening to the basement
can allow propane leaking in an upstairs room, to gain adequate access
to the basement space to cause a problem.
The bottom line here is that propane fueled exploding houses are
rare, and getting to that point takes a relatively major problem in
the tank setup before you go boom. But nevertheless, it CAN happen,
somewhat more easily than similar sorts of accidents with other fuel
gases. It’s about the same as having a gas fired oven in the kitchen,
the old types without safety valves, such that if you close the doors
and windows, turn on the gas with the oven door open, light the stove
pilot but not the oven, and then leave the room sealed, eventually
your kitchen will go boom too. Now lots of folks have accidentally
left an oven or stove burner on without blowing up the kitchen. but
every now and then… Propane accidents are rare. But they can
happen. the level of risk depends quite a bit on your exact setup,
the layout of your house, the condition of your equipment, and how
careful/paranoid you are about how you use your equipment.
I, for one, have a barbecue type propane tank in my basement
workshop. It’s a reasonably well ventilated workshop, the water
heater is electric, not gas, and I’m quite careful with my tanks.
Plus, it’s just me. No children to fool with things. I don’t feel
there is a problem there. But for some people, propane will not be an
intelligent choice. heck, for some folks, any sort of torch in the
house may be unwise (grin…).
With acetylene, there are a couple major differences. Like propane,
acetylene is contained in the bottle as a liquid. (Propane is
actually liquified, while acetylene is in solution in acetone). The
tank pressures are relatively low, and thus safe (as compared to
oxygen tanks, which require quite careful handling). But the tanks
themselves are tall and narrow, like oxygen. So though the tanks are
reasonably safe, they still must be secured, either to a cart, or
chained in place, so they cannot tip, etc. Propane tanks are more
stable, just based on their low squat shape, so need less restraint
or bother in the setup. The main difference safety wise between the
two is that acetylene gas has a quite small molecule, and the gas is
light, and dissipates quite rapidly in air. Plus, like propane, it is
manufactured with an added odor, so that it’s quite noticeable when
there is acetylene in the air from a leak. Because it dissipates
quickly, leaks are noticed quickly. And because it dissipates, rather
than sinking to the floor, it is much harder to get enough of a
concentration from a leak to be explosive. In a small closed room,
it can be done. But you need much more gas to leak, and the room must
be more tightly sealed. All in all, it’s very unlikely that this
would happen.
As a fuel gas for jewelry work, acetylene is also quite different
from propane. Acetylene is, to put it simply a really dirty gas.
Burned without enough oxygen, it sends little bits of soot flying all
over the room. makes a mess. Burned with enough oxygen, it’s a very
very hot flame, sometimes too hot for some types of work. You get
around that by using smaller torch tips, and for many tasks, this is
just fine. But you cannot, for example, get as good results with
platinum work using acetylene, since the excess carbon in even a
slightly oxidizing flame can cause problems with the platinum. Small
torches with acetylene work fine for general small work in gold, but
working silver with acetylene and oxygen can be a bit more difficult
than with gasses like propane or natural gas, which burn cleaner, let
you use a gentler larger flame if you like, and generally are more
suited to working cleanly.
If ALL you want to work with is silver, especially general
fabrication work, the acetylene may well be a very good choice, since
the air/acetylene torches like the Smith handi heat or the prestolite
type torches, produce a very nice flame that’s well suited to silver
work. Quite different than the flames from oxy/acetylene equipment.
You should also be aware that you have other quite viable options as
well. Although natural gas is more familiar to us coming from the gas
company, and residential gas lines are usually not high enough gas
pressure to run a torch well, you can also get natural gas in
compressed tanks, looking quite like the oxygen tanks. Natural gas is
a very fine fuel gas for jewelry work, much like propane, but it’s a
lighter gas, and does not present the specific risks that propane
does. MAPP gas is a mixture of gasses, presenting some of the best
of both acetylene and propane, in a form that also is much safer than
propane alone, and without either the overly high temps or the mess of
acetylene. It can be burned either with air, much like acetylene in a
prestolite torch, or with oxygen. Both MAPP and bottled natural gas
will cost more to run than propane, and maybe even acetylene. But
both work quite well, and some folks like one or another quite well.
If I could not feel OK with the propane tank in my basement, I’d be
using bottled natural gas, rather than acetylene and oxygen, though I
do have an acetylene B tank running a Smith handi heat, in addition
to my more frequently used torches. Like I said, it’s one of the best
torches for silver fabrication.
By the way, on the subject of tank safety. one often overlooked topic
is the oxygen tank. In my view, the oxygen tank represents a greater
risk than a propane tank ever would. With the gas tanks, you must
leak enough gas to form a flammable mix before anything can happen.
With oxygen, any leak increases oxygen levels, and if this occurs to
more than a minor degree, then any combustion in the room will be
accelerated. More important is the fact that a newly filled oxygen
tank is filled to a pressure of about one ton per square inch. think
about what happens if you accidentally drop such a tank in a way that
breaks off the neck/valve of the tank. If you open a gap in the top
of the tank of a square inch in area, then you’ve created a rocket
motor with a ton of thrust in the other direction. The risk is if you
tip over a full oxy tank, and hit the valve, cracking it
significantly. The pressure completes the job, blowing the valve off,
and the tank then accelerates VERY quickly, with a very great amount
of force. Tanks in that condition can knock down walls and fly
surprisingly large distances, and generally cause a great deal of
damage. And since there is usually a human involved in dropping or
knocking the tank over, if that hapless soul happens to be on the
wrong side of the tank when it takes off, it can easily kill. Even
normal use of the tank when it’s properly chained in place so it
cannot fall over, can be dangerous. The regulator, on it’s high
pressure side, where the adjustment knob is, is holding back a very
high pressure gas. If the regulator is faulty, then it’s possible for
it to burst from the pressure. Flying parts can be moving fast enough
to cause injury. The adjustment knob or T bar itself can be shot out
fast enough to take out an eye or worse. And if some idiot is dumb
enough to try and oil an oxygen regulator that seems sticky, the oil,
exposed to high pressure oxygen, can spontaneously combust or explode,
again destroying the regulator, and potentially causing a great deal
of damage to anyone close by. And for what it’s worth, I know of more
accidents cause by oxygen tanks than propane tanks. Think about it.
That oxy tank, when full, represents an enormous amount of pressure
and energy that can be instantly lethal if the wrong things happen at
the wrong moment.
Now that I’ve scared you about the oxy tank, sit back and relax.
Because the truth of the matter is that properly used oxygen tanks are
generally safe enough, and accidents with them are quite rare.
nevertheless, they DO happen, now and then, just as propane accidents
happen now and then. In most cases, the accidents are the result of
negligence, ignorance or carelessness, and are preventable by proper
maintenance, proper procedures in the use of the equipment, and
reasonably prudent attitudes. If you want to use a propane tank, you
need to be aware of the possible dangers, and make the decision
intelligently. And if you set one up and use it, you need to do so
with the care and respect required of any potentially dangerous piece
of equipment. I know many jewelers who’ve set up propane tanks. I
have never heard of any actual jeweler who’s had a problem/accident
with it, though we’ve all heard generic horror stories about what
MIGHT happen, or may have happened once to someone who we’ve heard
about, but somehow nobody actually knows who this victim really is…
While a due respect for propane is needed, don’t automatically go with
the knee jerk reaction of “OH my ghod, this is much too dangerous”.
It doesn’t have to be.
Peter Rowe