Carbon Monoxide Leak

17 Mar 2020
Reaction score
United Kingdom
I had a boiler service approx a month ago on my rented property. This showed everything to be ok and quoted a co/co2 ratio reading of 0.0009.
Last weekend the carbon dioxide alarm went off and was attended to by the emergency services and the boiler was turned off. My tenant was informed that it could not be turned back on unless it has a gas safety check and was signed off. The company who did the original safety check returned to check the boiler and found a CO2 level of 9.6. Not only this but there was a considerable of rust within the boiler where the CO2 has been leaking.
I am not very knowledgeable with plumbing and therefore would just like to ask if it is possible that such a level of rust could occur within 1 month, surely this should have been picked up at the annual service of the boiler.
Could anyone please advise?
Sponsored Links
Ok, firstly you’re mistaking Carbon Dioxide for Carbon Monoxide, which is odd, as you’ve put it in the title. Yes if the boiler is condensing inside the boiler, can set the alarm off and cause rust, in possibly less than a month. What boiler is it, is the alarm in date? What alarm is it? Eg Aico, can you download any data from it? It depends if it was rusty at the time of inspection. Is it definitely the boiler at fault?
Thank you Novice, yes sorry I meant carbon monoxide. Yes the alarm was in date - just, and has now been replaced and data can't be downloaded from it. I would say that the boiler is at fault if it is leaking co2 and is very rusty. Yes I am confusing CO2 with carbon monoxide, the CO reading is 100p.
I am more concerned about whether the original service and check was carried our correctly as there does seem to be quite a build up of rust in one month. My tenant tells me that the safety check did not take as long as it normally does so I am not sure how thorough it was.
wendy Green, good evening.

Clearly there is something amiss here, and at this point I freely admit I am not a gas service engineer

If it were me, I would be changing the company that undertakes the servicing of the boiler.

Gas Safe Engineers and Servicing of Boilers is governed by the "Gas Safe Register" [an on-line register] where you can look up the name of the company undertaking the work and because all Engineers have a unique number you can see if the person who undertook the original service is a registered person??

More knowledgeable board members will definitely have more information on this topic, with especial regard as to how to make a complaint to the register, why? because if this "event" had continued then there coud well have been a fatality?

Sponsored Links
Some boiler services are actually boiler ‘MOT’
A proper boiler service would have picked up the issue you highlight.
Rusty combustion chamber suggests the boiler was only probed for combustion readings which indicate combustion process was sound. Rust may well be due to internal leak, leaking of condensate or rain ingress any of which a proper service would have picked.

Did you get a landlords gas report? If yes, it is a safety check, not a service
What boiler is in the property? A mm odern condensing boiler can rust very quickly, also did you have a gas safety check only recently or an annual service aswell?
The gas safety check was carried out at the same time as the boiler service. It is a Main combi boiler.
If you boiler started leaking carbon monoxide (CO) and it was supposedly serviced a month ago then I would certainly be questioning whether it was performed correctly. Even if there was a condensate leak into the boiler case, it wouldn't rust through that fast. If the combustion space/case was rusted then the service should have found that and it should have been identified to you.

The readings that you were given has nothing to do with whether the boiler is still room sealed or not. Obviously if the CO detector has activated then there is a leak from either the flue or the combustion chamber/case into the room and that needs identified and fixed, if it can be.

Was it serviced properly ..... I'd be getting a second opinion
Thanks Rob, it is debatable whether it was serviced correctly in the first place. I am having a new boiler fitted today by another company so it will interesting to hear their view when they see the amount of rust in the boiler. Maybe it has happened very quickly, the guy who did the service came back and checked again when the alarm went off. He advised that corrosion can happen very quickly from the stuff that was leaking..I am dubious looking at pics of the boiler which my tenant sent me that such a build up can occur within a month.
It's very rare that a boiler casing the time that happens failure of internal components has nomally shut the boiler down.
Rust inside boiler casings is quite common and once the source is repaired does not normally cause further issues but should be monitored during annual servicing.
Any poor combustion due to leaking seals etc and re-circulation of combustion gasses would normally be contained within the sealed chamber of the boiler/flue and remain safe.

In my experience every case of a carbon monoxide alarm operating has been due to either...
An alarm being old and out of date
Contaminated with cooking fats etc
Incorrectly sited
Detecting cigarettes or similar

Unless you post pictures of the rust, boiler casings, position, flue and CO alarm no one can really say one thing or the other.
Some engineers will use a tiny spot of rust to condemn a boiler in order to get a new install, others will be more rational and use sensible judgement.
You might like to contact the boiler manufacturer and ask them for their opinion about whether it could have deteriorated so quickly. They might even want to have a look at it - has it been taken away?

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links