DH has often noted that there's a faint smell of chlorine/bleach in the house when he comes home after I've had a long session at the torch. Finally I decided to look it up and found a thread in the Lampwork ETC archive where it says the chlorine smell comes from NO emissions that aren't properly vented and that it's quite bad for your health :o
Oops. I do have ventilation and as far as I can tell it "catches" the fumes, but obviously I can't "tell" well enough :( I have a duct that is pointed toward the flame and (simple) smoke tests have shown it catches the exhaust, but maybe I need a hood to catch all of the NO? And/or a stronger duct fan? I got the strongest I could find at the hardware shop. Perhaps I should go to a specialist?
After having read the thread at LE I will not even THINK of lighting my torch again until I have this sorted :P
I get the smell of paint in my shed when I have been torching. I can only presume that the heat just brings it out. I have a Carbon Monoxide monitor, so the ventilation must be working.
I think the first question is how strong is your fan? Here at least the stronger fans tend to be from hydroponics suppliers for grow room ventilation. Hoods do help but might not be necessary, depending on our setup.
(I got a Systemair LTI RVK 200 L1, which is 950m3/hr. That seems to be on the high end of what we use here, but on the "just about good enough" end of LE recommendations, just so you know!)
My fan is about 300 m3/h, is that way too low then?
It is quite low (they talk in cfm over there, and 1m3/hr is 0.59cfm, so yours is about 177cfm if you want to compare with what they're saying).
I used the hood calculations to work out what I needed though, since I built a barley box. Those say you want 100cfm per square foot of hood area. For the non-hood way of doing it, I'm not sure what the numbers should be.
I can't find any duct fans of that capacity, the one I have seems to be at the upper end of what's available here :( Seems like I would have to get a fan that's mounted on the wall outside. They don't cost more than the duct fan did, but we'd have to get someone over to install the electricity for it since it's outdoors :-\
Hmm, Systemair are based in Sweden, so I would have thought *someone* over there would have their fans!
We got a cooker hood that is 500 cubic meters/hour.
that smell might just be what they put in the gas and it gets stonger sometimes towards the bottom of the bottle
if you have covered all your bases re leaks,ventilation (in and out of the space ) and have a monoxide detector etc etc and you feel ok after a session ie no headaches ,cough etc etc then everything should be ok
Do a smoke vent test again to make sure and tweak if nead be
MAKE SURE YOU BURN OFF THE GAS IN THE PIPES AT THE END OF A SESSION
there is a laod of chemical stuff about NO on wiki ,looks like there are several types so make sure you are panicking about the right one before you go spending a fortune on new vents etc ! (could not really understand it but ...)
the americans can be a bit '' bee in the bonnet'' when it comes to health and safety (not knocking health and safety just they can be a bit OTT)
It's not the gas smell, it's clearly a chlorine smell and the gas smells different. I've checked for leaks and I have a gas leak detector close by that would go off if I had leaks (I've tested it and it's fairly sensitive). I always burn off the gas and I make sure to light the torch as soon as I turn on the gas so that I don't leak a lot of gas before lighting the torch.
The smell is just as described in the threads I've found about NOx. I don't feel it when I'm at the torch but DH notices it when he gets home hours later and if I go out for a while and come in again I can smell it.
I don't have a CO detector though. Before I had my current fan I got headaches after torching for more than an hour. I don't get that anymore so I assumed I was all right. I often feel a bit dazed and light headed at the end of a session but that's just as likely because I go too long without eating and perhaps don't drink enough either ;) I frequently feel the same way after 4 hours at the computer...
One thing to check is whether you have enough 'good' air coming into the room to make up for the bad air which the extractor removes - that can make quite a big difference.
Natural gas (as used in cooking) produces a lot of NOx - and although this issue is raised in the scientific literature, it doesn't seem to have resulted in legislation.
Quote from: flame n fuse on June 04, 2012, 09:45:02 PM
One thing to check is whether you have enough 'good' air coming into the room to make up for the bad air which the extractor removes - that can make quite a big difference.
I was just thinking about that. I used to open the window in the next room but for some reason I've stopped doing that (probably some time during winter). I should start doing that again.
We will also try rebuilding the duct and building a hood or funnel similar to the one Tuffnell has on their extraction kit in order to improve the extraction.
Speaking of Tuffnell, the fan in their extraction kit extracts 110 m3/h and they say it's enough for a garage, shed or spare room. My studio is in a room much smaller than a garage so my 360 m3/h fan should be more than enough if Tuffnell's fan is enough.
As long as you are:
- Extracting a larger volume of gas than the torch produces
- Capturing all of the output of the torch
- Replacing all of the extracted gas with make-up air
- breathing from an airflow which does not originate near the torch
Then your extraction is entirely sufficient.
But only if
all of the above points are satisfied; nothing else is required.
There is a lot of mis-information floating around on the world-wide interweb, mostly of the 'if-your-extraction-can't-suck-your-lungs-out-it's-not-good-enough' variety. Common sense will tell you that all you need to do is a) capture all of your exhaust gasses, and b) ensure you can replace what you extract.
Having said that, each situation is unique (overhead hood, local extract, baffled hood, cooker hood, barley box, against wall, on island bench, etc.), so an awareness of the symptoms of breathing NOx is important; headaches, dry/scratchy throat, coughing, and That Smell all tell you there is something wrong with your extraction. Think about how the air and exhaust gasses are flowing, adjust your setup, and try again.
Incidentally, you will very quickly become accustomed to the smell of NOx - someone coming in with a fresh nose will smell it much more strongly, so it will often be someone else who brings the problem to your attention. And, it seems that the most common problem is with a lack of make-up air...
Sean
Sean, that is the most informative, shortest, and best understandable post I have seen on ventilation - thank you!!! :)
Thank you, Sean :)
Fortunately the only symptom I've noticed is the smell.
With lots of help from DH I've now got a hood, a new duct and a new ventilation outlet cover ;D Simple smoke test shows it catches everything that isn't clearly outside the hood, which would be quite a bit off. On Monday I'll do a "test drive" and see if this is enough or if I should start looking for a stronger fan as well.
Noora, have you checked your torch for leaks? I installed my ventilation and decided to hook up my mid range at the same time, very quickly I noticed a gas smell but the smoke tests came out clear. I checked the connections and the hoses and they were all fine. It was only when I checked the torch and systematically sealed every joint I realised it was leaking out of one of the propane knobs on the torch.
A seal of blu tack and it has been fine ever since.
It is not gas smell (the smell they add to the gas here is quite different from chlorine) and I have checked for leaks :)