My wife works in a church which has experienced the smell of gas several times (both this year and last) typically at this time of year when the system is first started. The building is on LP gas (Liquid propane). There are three boilers and perhaps a hot water heater or two in the wing of the building where the smell is strongest. LP smells like rotten cabbage.
The gas supplier says this smell is because the pilot light has gone out, and the smell is to alert you to this fact. They claim it is perfectly safe. Is this true? I’m not convinced. Isn’t the piping at the pilot light designed to STOP gas flow once the flame goes out (via a venturi, I believe). If the gas company is correct, then what, exactly, is supplying the smell to alert you? Is it, perhaps, residual LP in the line? (Isn’t this still a potential danger?) Or, is gas still flowing from the supply tank? That supposedly-safe smell to alert you must have some not-so-safe source, right?
If you’re not convinced the maintenance staff know what they’re talking about, you should call the fire department and/or the LP supplier and tell them of the presence of strong odor of gas.
The fire department is more than happy to investigate the smell of gas, rather than respond to a fire/explosion.
All the heater (as opposed to stove) pilot lights I’ve dealt with use a thermocouple, which shuts off the pilot light gas when it’s not heated by the pilot light flame. I would expect building codes to require these. I’ve never heard of the odor being considered normal.
I would find it plausible that the having the odor briefly when a dormant system is restarted might be normal, but absolutely not for the reason that a pilot light has gone out.
Surprisingly, it is the LP supplier claiming it is perfectly normal, but I don’t buy it! I think they just want an easy-out. Not only is everyone’s safety at risk, but this is a preschool setting! People’s most-precious possessions are at risk!
Since I do not believe the LP Supplier (although long-standing in the business) is giving this proper attention, I think it might be best to ask the fire dept to come, too. Do they handle such issues and do they come equipped with handheld “sniffer” instruments to investigate?
In general, IMHO, I cannot believe it is normal. I can say that, during one epsiode, one teacher coming in with her class off the playground reacted with “Wow, I smell gas…” So, it’s not like a faint odor like “Hmm, I think I smell a hint of gas…” And, while others’ noses in the building may be “immune” to the smell… one coming in from outside should not, IMHO, have such a surprise reaction!
I believe it is also possible that two things are happening: (a) the pilot problem may have been corrected hence the LP rep says it’s not a problem, but (b) gas pockets have meanwhile collected in low-traffic areas, such as the vestibule allowing access to the playground. It is possible such areas are not being ventilated by propping open the door, for example, because everyone is thinking “it’s ok” and they’re operating in a “no need to panic” mode.
All thoughts appreciated…will continue to dig further.
Does this happen only at the first start up of the boilers at the beginning of the heating season? Or is the smell of LP present anytime the boilers are used?
Is the LP used year round for hot water? If so, is there a smell of gas when the boilers are not used (i.e., summer)?
Older equipment has a pilot light that is ‘on’ even if it is not ignited, my parents have a stove and oven w/ this ‘feature’. The reasoning is that the pilot light is so small it on’t allow a explosive amount of gas to escape if it’s off but you will smell it and relight the appliance (after shutting it down to clear the non explosive gas mixture :rolleyes: ). The main burner won’t ignite however unless there is a pilot light actually lit either by a theromcouple or a heated bar when elonggates when heated and opens the valve.
a) We know the building was completed in stages. But, we believe these boilers are for the whole building. I know there is a kitchen area elsewhere in the building, and IIRC, there is at least one hot water heater there. The kitchen area is on the same level as the church office. They smell nothing on that level.
b) To the best of my knowledge, the boilers are used for the HVAC system. This problem seems to only arise at the start of the heating season - like now.
c) I don’t know if the boilers are natural or forced draft. I can ask, but isn’t that a ventilation issue? Or, are you thinking that fugitive fumes should be vented out of the building, perhaps?
Hmm…interesting. This building may be ten years old, but from what I hear about the HVAC industry, bad practices are hard change and phase out. So, what you say could be a possibility. Still, it’s not too comforting, is it? At least, thanks to indoor smoking laws, people don’t come walking into the building with a lit cigarette! I’ll see what more I can find out. - Jinx
Just because you can smell gas doesn’t mean it’s dangerous. What you’re really smelling is an additive introduced to impart an easily detectable odor to the otherwise odorless LPG, and it is detectable at levels of only around 6 PPM, far below the LEL. Approaching the LEL (lower explosive level–something like 19,000 PPM or so for LPG at 70 F) of LPG the smell would be overwhelmingly strong, to the point you’d more or less be forced out of the building. Much below that level, even lighting a match won’t cause an explosion, though you’d be wise to avoid sources of possible ignition in the presence of a very strong gas smell, until the cause can be located and dealt with. Oddly enough, even with ideal explosive mixture of LPG and air, a lit cigarette is not a potential ignition source–though what might be used to light the cigarette is.
Boilers and hot water heaters should not continue to flow gas when pilot failure occurs. They all use a feedback system to verify main burner flame. Failing that verification, no gas flows.
Only cooktops (IME) have standing pilots which can be extinguished and allow gas to flow.
I’d be interested to know the draft calculations of the entire system. What was the original appliance for which the chimney was sized? How has that equation changed over time? Is that calc valid for the current load?
A forced draft boiler would have a purge cycle that would remove any fuel in the boiler prior to attempting to light the pilot. A natural draft would not have this purge cycle.
I sort of doubt that a modern boiler (did you say the building was 10 years old?) would have a pilot light that was on all the time. Instead, it would have a spark ignitor that would light the pilot, and then verify that the pilot was lit (using perhaps an IR detector) before turning on the main gas valve. At start up, there may be trouble getting the pilot to stay lit resulting in a gas smell.
Other possible causes, of course, are leaks in the piping downstream of the gas supply shut off valve, or the pressure regulator venting (although this should be piped outside).
This sort of thing is impossible to diagnose over a message board. Forget about the LP supplier, and for now, forget about the fire department. Instead, call a boiler technician to check out the boilers.
By the way, who starts up the boilers at the beginning of the heating season? The LP supplier, a boiler technician, the building custodian, or someone else? Who does the regular maintenance of the boilers?