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Dr Bob

Carbon monoxide safety on NBs

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I dont want to be alarmist but....I've just had a bit of a shock.

The glass on our stove has been getting a bit (lot) black so decided today to try and clean it. Usually this is easy when cold but the stove has been on for weeks so needed to do it hot. The fire was at the low end of its heat (first thing in the morning) and I opened the door wide. No smoke, looked like it was burning clean. Spent about 10 mins scraping the window, emptied the ash but didnt immediately put the ash can out the front (like I normally do - because of CO)  and banked the fire up and shut the door.

I happened to glance at the CO monitor and it was showing 174ppm! Eeeek. The other monitor half way down the boat was showing 134ppm. Opened all the windows and within 5 mins the CO level was down to zero. Ok, everyone safe (although the duck is looking a bit yellow) but why didnt the alarm on the two units go off? They were Kidde 7dco units (2 years old). I checked the tinternet and that was reporting the US regs for CO is to remove peeps from confined environments if levels get over 100ppm. The danger is a time thing so 50ppm for 8 hours exposure is dangerous so 170ppm for 10 mins shouldnt be a problem. I've put a table of effects of CO below. CO is cummulative in the body. The molecules latch onto the red blood cells and do not come off.

Maybe these alarms have to exceed a certain ppm for a certain time before they go off but I have just been assuming they would alarm when the ppm got high so have never seen a problem when sorting the stove. I always put the ash outside straight away because of the potential for CO coming off the ash and dont leave the door open more than is needed but that excursion up to 170ppm is not good.

I've emailed Kidde to ask them about the alarm settings. Maybe these alarms do sound after 5 mins of that exposure but I dont like the idea of 174ppm without an alarm. It is quite interesting to see how far down the boat the CO travels.....but that is not surprising as I do have a decent ecofan!?

Has anyone looked at their monitors when doing their fire?

 

Screen Shot 2019-12-12 at 10.16.45.png

Screen Shot 2019-12-12 at 10.13.56.png

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3 minutes ago, Dr Bob said:

I dont want to be alarmist but....I've just had a bit of a shock.

The glass on our stove has been getting a bit (lot) black so decided today to try and clean it. Usually this is easy when cold but the stove has been on for weeks so needed to do it hot. The fire was at the low end of its heat (first thing in the morning) and I opened the door wide. No smoke, looked like it was burning clean. Spent about 10 mins scraping the window, emptied the ash but didnt immediately put the ash can out the front (like I normally do - because of CO)  and banked the fire up and shut the door.

I happened to glance at the CO monitor and it was showing 174ppm! Eeeek. The other monitor half way down the boat was showing 134ppm. Opened all the windows and within 5 mins the CO level was down to zero. Ok, everyone safe (although the duck is looking a bit yellow) but why didnt the alarm on the two units go off? They were Kidde 7dco units (2 years old). I checked the tinternet and that was reporting the US regs for CO is to remove peeps from confined environments if levels get over 100ppm. The danger is a time thing so 50ppm for 8 hours exposure is dangerous so 170ppm for 10 mins shouldnt be a problem. I've put a table of effects of CO below. CO is cummulative in the body. The molecules latch onto the red blood cells and do not come off.

Maybe these alarms have to exceed a certain ppm for a certain time before they go off but I have just been assuming they would alarm when the ppm got high so have never seen a problem when sorting the stove. I always put the ash outside straight away because of the potential for CO coming off the ash and dont leave the door open more than is needed but that excursion up to 170ppm is not good.

I've emailed Kidde to ask them about the alarm settings. Maybe these alarms do sound after 5 mins of that exposure but I dont like the idea of 174ppm without an alarm. It is quite interesting to see how far down the boat the CO travels.....but that is not surprising as I do have a decent ecofan!?

Has anyone looked at their monitors when doing their fire?

 

Screen Shot 2019-12-12 at 10.16.45.png

Screen Shot 2019-12-12 at 10.13.56.png

Your not Kidding.

Mines an absolute Angel.

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I think you make the point that a fairly high reading for a short while isn’t a problem. You don't really want the CO alarm sounding every time you open the stove door. You only want it sounding when there is risk to human health, which is the cumulative product of CO concentration and time.

 

Our monitor does sometimes go up a bit when I do the fire, but it is not close to the stove - stove is at the front and CO alarm is near the exit from the kitchen towards the bedroom (open plan as far back as corridor to bedroom).

 

Of course a display is optional on a CO detector, plenty don’t have one.

Edited by nicknorman

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My fireangels (I have two) work like this:

 

The Alarm will sound:
• Between 60 and 90 minutes when
exposed to a minimum of 50ppm of CO.
• Between 10 and 40 minutes when
exposed to a minimum of 100ppm of CO.
• Within 3 minutes when exposed to a
minimum of 300ppm of CO.

In test mode, the alarm goes off as soon as the level gets to 50ppm, rather than waiting for an hour.  So with the levels you quote the alarm would have gone off after say 10-15 minutes?  From your description it sounds like you noticed the reading only a few mins after filling the ash tray?
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57 minutes ago, nicknorman said:

I think you make the point that a fairly high reading for a short while isn’t a problem. You don't really want the CO alarm sounding every time you open the stove door. You only want it sounding when there is risk to human health, which is the cumulative product of CO concentration and time.

^^^^^ This. 

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There seems to be a distinct lack of care for the Duck in this thread!

 

On a serious note it goes to show just how important it is to have alarms fitted! There are two in Python's relatively small cabin. One of them is deliberately placed at a similar height to someone's head if they were sleeping in the cabin.

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1 hour ago, Scholar Gypsy said:

My fireangels (I have two) work like this:

 

The Alarm will sound:
• Between 60 and 90 minutes when
exposed to a minimum of 50ppm of CO.
• Between 10 and 40 minutes when
exposed to a minimum of 100ppm of CO.
• Within 3 minutes when exposed to a
minimum of 300ppm of CO.

In test mode, the alarm goes off as soon as the level gets to 50ppm, rather than waiting for an hour.  So with the levels you quote the alarm would have gone off after say 10-15 minutes?  From your description it sounds like you noticed the reading only a few mins after filling the ash tray?

Ah, that sounds more like it. Shame the Kidde alarm does not have that data easy to hand.

I guess our meters were over 100ppm for about 5 minutes -pretty certain it was the door open rather than the ash (but the ash is a hazard for CO), not long enough to set the alarm off.

 

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1 hour ago, Dr Bob said:

..... -pretty certain it was the door open rather than the ash (but the ash is a hazard for CO), not long enough to set the alarm off.

 

You are probably correct, but it is actually remarkable how much can come from the ash if you don't get it outside straight away.

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2 hours ago, Dr Bob said:

Ah, that sounds more like it. Shame the Kidde alarm does not have that data easy to hand.

The Kidde alarm might be good to learn on, but I think you need a grown up version in a boat. ;)

 

 

More seriously, my ash and cleaning routine sounds to be similar to yours but, for comparison, the Fire Angel CO alarm adjacent to the stove in the forward saloon is currently reading 0ppm with a recorded peak of 10ppm over whatever longer monitoring period that might be. My stove had a good hook out  like yours this morning. The bedroom one down aft reads 0ppm with a 0ppm historic peak.  Don't write your high readings off as a "they all do that, Sir" thing too soon. Can't be too careful here, Doc. :)

 

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Ditto (more of less) Sea Dog's post.

 

I have a Kidde near the stove and a Fire Angel in the bedroom (or vice-versa), both with displays, and open the stove in the morning to let the door cool down before cleaning and empty the tray while it is doing so. I always riddle and/or poke around with a poker AFTER emptying the tray and closing the door and then riddle/poke again but leave that ash in the pan for at least another hour or two before emptying it out. That seems to reduce the amount of CO given off as both alarms continue to read zero throughout. I know they work though as I have seen both register small amounts of CO in other situations and also sound the alarm when one of our batteries went into rotten egg mode as it died.

 

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2 hours ago, Sea Dog said:

More seriously, my ash and cleaning routine sounds to be similar to yours but, for comparison, the Fire Angel CO alarm adjacent to the stove in the forward saloon is currently reading 0ppm with a recorded peak of 10ppm over whatever longer monitoring period that might be. My stove had a good hook out  like yours this morning. The bedroom one down aft reads 0ppm with a 0ppm historic peak.  Don't write your high readings off as a "they all do that, Sir" thing too soon. Can't be too careful here, Doc. :)

 

The Kidde alarms we have that I think are the same as Dr Bob has posted read zero until CO is measured at 30.  If the rise higher, once they drop back beyond 30 they immediately sow zero, even if you are actually constantly living with a number in the 20s.

That has never seemed idea to me.

Can you confirm that the Fire Angel ones do record when the level is above zero, but under 30, please?

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1 hour ago, alan_fincher said:

Can you confirm that the Fire Angel ones do record when the level is above zero, but under 30, please?

I think so Alan - as I say, the one by my stove is reading zero at the moment, but when changing between temperature and CO displays, it tests the alarm and displays an historic maximum CO reading. Currently, that reads 10ppm so it would seem to go down at least that far. The models I have are the CO - 9D. I've had them a wee while so there may be a newer version now as, whilst they're BS EN 50291 -1 and -2, they are to the 2010 standards and pre-date the BSS regs.

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9 hours ago, Scholar Gypsy said:

My fireangels (I have two) work like this:

 

The Alarm will sound:
• Between 60 and 90 minutes when
exposed to a minimum of 50ppm of CO.
• Between 10 and 40 minutes when
exposed to a minimum of 100ppm of CO.
• Within 3 minutes when exposed to a
minimum of 300ppm of CO.

In test mode, the alarm goes off as soon as the level gets to 50ppm, rather than waiting for an hour.  So with the levels you quote the alarm would have gone off after say 10-15 minutes?  From your description it sounds like you noticed the reading only a few mins after filling the ash tray?

 

That's because CO poisoning is a dose-response thing.  As NIck said, it's a function of both concentration and duration of exposure.

 

 

 

SO DON'T PANIC!!;

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2 hours ago, Machpoint005 said:

 

That's because CO poisoning is a dose-response thing.  As NIck said, it's a function of both concentration and duration of exposure.

 

 

 

 

I did actually say it was time related in the OP but was concerned it got to 174ppm which exceeds the US 'get peeps out of confined spaces' edict.

Kidde came back to me this afternoon and said that the meters conform to the EN standard which is the times and amounts in the fireangel as posted above......so at 174ppm they would go off after 10 mins.

Still at least I now know i) my meters are working (both of them)  and ii) dont leave the fire door open too long.

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20 hours ago, bigray said:

...  On a serious note it goes to show just how important it is to have alarms fitted! There are two in Python's relatively small cabin. One of them is deliberately placed at a similar height to someone's head if they were sleeping in the cabin.

This (for CO alarms).   CO is only slightly lighter than air, so detectors can be placed at any height and still be effective; somewhere relatively close to the stove / ash bucket is good  - but obv. not so close that it goes off repeatedly.    Smoke / heat alarms OTOH are best placed high up - ideally on the ceiling, away from walls.

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Bob you keep saying coal, do you mean coal or a smokeless?

i say this because we never burn housecoal now on the boat, even in the range in the back cabin. The reason being we found many years ago slow combustion of coal blocked the flue , where it is formed to fit the boat. I always assumed with 2 bends the exhaust gas slowed at the bends, and with the high particulate level of coal the flue got down to a couple of inch  internal diameter, causing blowback.

since running only smokeless this issue is reduced as it burns to a white residue.

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1 hour ago, roland elsdon said:

Bob you keep saying coal, do you mean coal or a smokeless?

i say this because we never burn housecoal now on the boat, even in the range in the back cabin. The reason being we found many years ago slow combustion of coal blocked the flue , where it is formed to fit the boat. I always assumed with 2 bends the exhaust gas slowed at the bends, and with the high particulate level of coal the flue got down to a couple of inch  internal diameter, causing blowback.

since running only smokeless this issue is reduced as it burns to a white residue.

Hi Roland, Happy new year to you down under.

I use the word coal as it only has 4 letters in it. ? No, its excel that I have been using this winter (mostly.....although I did get a few bags of supertherm early on when there was no excel left). For the last month I have been very critical of the excel as I kept getting a throat full of 'orrible smell. I thought  the manufacturers were 'at it again' giving us crap coal. Once the chimney was cleared, there is not a trace of that smell! I really have been a muppet! ? I should have recognised the symptoms of a blocked flue. Now the flue is clear, the fire is burning sooooo much better and not depositing dust all over the inside of the boat and poisoning us with CO. I really can't work out why I didnt twig it was the flue getting blocked. A lesson for everyone.

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2 hours ago, nicknorman said:

Probably due to the long term effects of mild CO poisoning!

Absolutely!?

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The more I learn the more amazed I am to have survived...when we were young and broke there was little knowledge about boat stuff. We installed fires  bodged up glass doors ,all without co2 monitors and smoke detectors. Ignorance is bliss.

dont need coal in gippsland at moment, its a bit smokey..

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How much, if any, of your flue pipe is insulated? The debate as to whether all the flue should be insulated will no doubt run forever but there is little doubt in my mind (based on decades of experience) that all the external section of pipe should be of the double insulated variety. The position of your blockage proves that point.

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