Gas Alarm

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Sailfree

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Got a Nereus LPG alarm and it's been going off.

Put my head beneath floor by position of sensor and cannot smell any gas at all. Lifted sensor head above floor and blown on it and still alarm flashing (I have silenced it with hush switch).

It's about 14yrs old.

Any idea how sensitive these LPG sensors are? Will they detect Gas when you cant even smell it?

Using camping Gaz cylinders that I believe are butane.
 
It’s not a combined LPG and CO one by any chance, is it?

I have had a gas alarm go off from contact-adhesive fumes before. Got any other volatile substance open?

I’ve seen replacement Nereus sensor heads for sale, which implies they might have a finite lifespan.

Pete
 
No date on sensor head £75 for replacement. About £250 for complete alarm. Head is a sealed unit.

Gas is off, sensor now above floor and still alarm flashing

No smell of gas.
 
I've never had a gas alarm, simply don't see the point. If you're vaguely sensible in your use of LPG, and turn things off properly, what's the risk? Does copper pipe suddenly fracture under zero pressure? Do fittings suddenly unscrew themselves?
 
If it's 14 yrs old its probably a pellister type which has a catalytic sensor in the head. These sensors have a finite life and eventually fail. Some of them can also be "poisoned" by the presence of silicone based products. The failure of the sensor on these devices normally results in an alarm as they are set up for "upscale" failure, meaning that a failed sensor will not go un-noticed.
 
pvb said:
I've never had a gas alarm, simply don't see the point. If you're vaguely sensible in your use of LPG, and turn things off properly, what's the risk? Does copper pipe suddenly fracture under zero pressure? Do fittings suddenly unscrew themselves?
Click to expand...

Gas valves leak, rubber hoses deteriorate and leak, diaphragms in regulators can fail and do fail and result in gas leakage. Thats the risk for me and I'd like to have knowledge of it before I switch electric items on and off or try to light the gas stove.
 
greeny said:
Gas valves leak, rubber hoses deteriorate and leak, diaphragms in regulators can fail and do fail and result in gas leakage. Thats the risk for me and I'd like to have knowledge of it before I switch electric items on and off or try to light the gas stove.
Click to expand...

Gas valves leaking in a vented gas locker won't be dangerous. Rubber hoses are date-stamped and we all know to check them routinely. Regulators are in vented gas lockers so leakage isn't dangerous. Unless your gas installation is very amateurish, there's no danger.
 
pvb said:
I've never had a gas alarm, simply don't see the point. If you're vaguely sensible in your use of LPG, and turn things off properly, what's the risk? Does copper pipe suddenly fracture under zero pressure? Do fittings suddenly unscrew themselves?
Click to expand...
I do not know !
However, some years ago, a liveaboard barge, up by Fishermans Wharf, in Penryn , Falmouth.
Exploded , during the night, killing a whole family & destroying a load of buisinesses.
There was one surviving daughter, who had been at a sleepover, with her friends !
I have no idea, what happened to her, afterwards !
So, yes, even at. 66, I am paranoid, about. turning gas on & off !
I was in Williams Boatyard, at the time !
The Bang, was incredible !
Initially I thought it was an IRA Bomb !

On a different note ? Could anyone, explain to me........ Why does a. CO2 alarm, have to be mounted about 6 ft over the floor ?
I dont get it !
C02, is. supposedly heavier than air ?
So, why in hell, would you mount a CO2 alarm, 3 ft above your bed height ?
Sorry
I have ignored all of those stupid CO2 alarm instructions !
I mount my CO2 alarms, around the. skirting boards, or whatever fancy name you want. to give, to the bottom of cabin berths !
 
Last edited:
STILL AFLOAT said:
I have ignored all of those stupid CO2 alarm instructions !
I mount my CO2 alarms, around the. skirting boards, or whatever fancy name you want. to give, to the bottom of cabin berths !
Click to expand...

Could it be because they are in fact primarily CO alarms and not CO2. CO is actually slightly lighter than air so alarms should be high. CO is a by product of combustion and is a lot deadlier than CO2. CO2 merely suffocates you, but CO binds to your red cells more tightly than Oxygen so even if they get your lifeless but warm body out of the CO atmosphere while you are still alive, and give you oxygen, you can still die because the Red cells keep hanging on to the CO!
Biggest risk? operating a gas cooker with insufficient ventilation.
Maybe the instructions aren't stupid?
 
CO is generated by a badly burning hydrocarbon source. As a result, the gas will usually be warmer than the surrounding air and thus rise.
 
CO2 is denser than average air density but that doesn't mean it sinks. If it did, we would all need to move to higher ground (and to the top of the mast at least) to escape the unbreathable lowest layer of the atmosphere.
 
Sailfree said:
No date on sensor head £75 for replacement. About £250 for complete alarm. Head is a sealed unit.

Gas is off, sensor now above floor and still alarm flashing

No smell of gas.
Click to expand...

Never assume. Never rely on your own sense of smell for gas detection.
 
STILL AFLOAT said:
I do not know !
However, some years ago, a liveaboard barge, up by Fishermans Wharf, in Penryn , Falmouth.
Exploded , during the night, killing a whole family & destroying a load of buisinesses.
There was one surviving daughter, who had been at a sleepover, with her friends !
I have no idea, what happened to her, afterwards !
So, yes, even at. 66, I am paranoid, about. turning gas on & off !
I was in Williams Boatyard, at the time !
The Bang, was incredible !
Initially I thought it was an IRA Bomb !

On a different note ? Could anyone, explain to me........ Why does a. CO2 alarm, have to be mounted about 6 ft over the floor ?
I dont get it !
C02, is. supposedly heavier than air ?
So, why in hell, would you mount a CO2 alarm, 3 ft above your bed height ?
Sorry
I have ignored all of those stupid CO2 alarm instructions !
I mount my CO2 alarms, around the. skirting boards, or whatever fancy name you want. to give, to the bottom of cabin berths !
Click to expand...

Already been mentioned, but its important - CO or CO2? Do you know the difference?
 
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