Acceptable levels of CO

[conny]

Had a smell of rotten eggs from the heating boiler last Friday morning so called the estate agents we rent from. They said they would contact landlady and get back to us. Three hours later I contacted BG for advice and within the hour they had an engineer out who said it was dangerous and isolated the boiler until an engineer came and checked it. He advised it probably couldn't be repaired as it was quite old.

Engineer turned up at 6.00pm and took it apart. Not sure what he actually did but after he put it back together he 'tested' it and declared it safe. I asked him if he had tested for Carbon Monoxide and he said he had tested for all leaks and everything was ok. Carbon Monoxide was peaking at 0.2 but steady at 0.1. I asked what this meant and he said you were allowed 40 parts per million as the upper limit so this was safe.

Boiler was not working over the weekend but we had a different engineer coming this morning to do a landlords safety check of all gas appliances. My house sharing partner explained what had happened at the weekend and that the boiler was not firing up. He tested it and ignited it before carrying out his safety checks. Within 10 minutes he had shut it down and condemned it as highly dangerous and unrepairable because of its age. He contacted me at work to explain and I asked him what the acceptable limits for CO where. He said there are NO ACCEPTABLE LIMITS, however, the reading should be no more than 0.008 (or possibly 0.0008 I'm not sure exactly) Our reading was 0.03 What do these readings mean?

How can one guy say its safe on Friday night and another condemns it first thing Monday morning when the boiler hasn't even been working?

 

[Dan Robinson]

These are combustion ratios - and the first guy that said 0.2 and 0.1 were ok should have his balls handed to him on a plate.

There will always be a reading, but you are confusing CO escapes with poor combustion.


What boiler is it?

 

[gasmanstu72]

the numbers you're quoting refer to the ratio between CO2 (carbon dioxide) and CO (carbon monoxide)

the engineer will have used a flue gas analyser, to sample the burnt gasses, if the ratio goes above 0.0080 (yours is 0.0300) he will need to investigate the reasons for it and repair if required. if no adjustments, service or repairs can make that reading drop he will have to class it as Immediately Dangerous and cut it off.

it sounds like you have an old boiler, there's not a lot that can be done to an old boiler in terms of adjustment, so it sounds like you'll be needing a new one if they cant get the parts

without going into too much detail there are acceptable limits, even a brand new straight out of the box will chuck out some CO

 

[conny]

Its a Myson Apollo and looks quite old.

The guy who said the readings were .1 and .2,when asked what the permissible limits were said something about being allowed 40 parts per million though I honestly don't know what he was talking about at the time. (He tends to waffle a lot )

Gassafe engineer who came today and condemned it has isolated it and put a big red/yellow sticker on it sating, "Gas ratio to high!!!"

Should add that the property is rented so I'm personally not bothered how much a new system will cost.

 

[hertsboilers]

Concentration of combustion products entering the premises outside the acceptable limits of BS 7967 e.g. CO greater than 10ppm and rising is classified as “Immediately Dangerous”.

Bear in mind at PPM (part per million) level, CO concentration can’t accurately measured. My Kane 455 says having an accuracy of +-10ppm while <100ppm. So a rising trend is a key factor.

 

[Dan Robinson]

A combustion ratio on 0.1 would not be under 40ppm.

Yes the Apollo is very old and quite likely to have a rotten flue. But that needs investigating.

 

[gasmanstu72]

On a new boiler there are adjustments that can be made to affect the ratios, but in your case there's nothing like that that can be done.

like Dan says, the flue is more than likely rotten through, meaning that the burnt gas on the way out is now mixing with the fresh air on the way in, causing incomplete combustion which sends the CO levels through the roof.

before it was cut off, did you see in through the sight glass where you can see the pilot? was it all orange and floppy? (the flame that is ) rather than a nice clean blue flame?

do you have a CO detector? they're well worth getting

 

[conny]

I was at work when the guy came today and apparently the flame was a steady blue. However, he said that just because it wasn't orange and wavering it was no indication that everything was ok.

I've tried looking through the sight glass in the past to see what colour the pilot flame was and, to be honest, it has been quite difficult to even see the flame never mind the colour.

Yes we have a CO detector and test it regularly. It is placed approximately 2 metres away from the boiler and not obstructed by anything such as walls or draughts.

Can someone post a pic of a sample gas check form to try and jog my partners memory as to what figures she was shown today? Are the forms a standard document with the tests in a set order or do different companies lay out their own designs of form?

 

[gasmanstu72]

the things you need to record are:

CO2 %
CO ppm
CO / CO2 ratio

 

[Dan Robinson]

There are no standard forms, but the numbers are the same across the analysers.

CO (ppm)
CO/CO2 Ratio
CO2(%)
Xs Air (%)
O2 (%)

There is no way you can get 40ppm and a ratio of 0.2

Lot's of engineers don't understand the numbers. And even worse think that 0.2 is lower than 0.004

 

[conny]

The form she was shown had quite a few items on it and these were supposed to have all been filled in though she can't remember how many actually were.

I thought if someone could post a copy of one it may help jog her memory.

 

[hertsboilers]

As gas engineers once reported smelling fume we have to measure flue gases and ambient CO level in the room.

gasmanstu72 and Dan were concentrated on flue gas analysis.

My point was on room ambient CO level.

Even one of the two failed, then your boiler is unsafe.

 

[hertsboilers]

Hi conny, what do you want? The boiler has already been classified as unsafe?

 

[Dan Robinson]

Indeed - and there were lots of Apollos, some with fans and some with without. Am involved (not so much now thank god) with a development with 300 or so of the things most of which are on SE flues, btu probably have every variant of Apollo installed

Ming is correct in asking about ambient CO levels, however, CO/CO2 ratios have naff all to do with ambient levels, so the visiting engineers are either disasters waiting to happen, or your partner is seriously mis remembering the events.

Does she not have copies of the forms?

 

[hertsboilers]

Ming is correct in asking about ambient CO levels, however, CO/CO2 ratios have naff all to do with ambient levels, so the visiting engineers are either disasters waiting to happen, or your partner is seriously mis remembering the events.

This case reminds me to do all FGA even on very old boilers.