Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

CO levels

John S_2
John S_2 Member Posts: 29
What is the acceptable CO level for a gas-fired appliance? I've heard that the local utility uses 400 ppm as the maximum acceptable reading but I have found that anything over 100 ppm is usually indicative of combustion issues. Oil or gas. Either too much excess air or too much fuel for the available air. I'd like some opinions,... having a friendly debate with a (sort of) colleague/competitor.

Also would like to reference OSHA and EPA standards as far as what is safe in the ambient air. I haven't been keeping up with it lately as I was out of residential service work for a time and mainly handled refrigeration and A/C issues. I think I remember it as OSHA was 35 ppm and EPA was 50 ppm (over an 8 hr exposure) but I could have it bass ackwards.

There was an error rendering this rich post.


  • John S_2
    John S_2 Member Posts: 29

    yeah, I kind of did have it backwards http://www.epa.gov/iaq/co.html

    There was an error rendering this rich post.

  • Tim McElwain
    Tim McElwain Member Posts: 4,628
    You are correct on the

    100 PPM and that is an air free reading and it applies to both gas and oil heating. The 400 PPM is an ANSI standard as an allowable level (it is really too high) and for gas cooking stoves the ovens under ANSI is 800 PPM. Unvented heaters is 200 PPM. All of that is too high. You found the other standards you were looking for.

    On some new Mod/Con equipment the manufacturers instructions should be followed for acceptable levels in a flue sample as some of them are slightly higher than 100.

    I have some manuals available for sale that educate on all aspects of combustion and combustion testing.
This discussion has been closed.