CO in plenum

[walker]

What is the amount of CO allowable in the plenum of a furnace.

I tagged a guy yesterday because I was getting 13ppm of CO in the plenum. I searched high and low for a visible crack in the exchanger but couldn't find a glaring crack. The heat exchanger itself was rusted to hell all along the tubing bends.

[Admin]

I don't know of any code or document that states allowable CO levels for fuel fired appliances in Ontario.

Clause 4.21.1 - Where the heat exchanger of a furnace installed in a dwelling unit is found to be defective, it shall be replaced.

The definition of defective is clear,

imperfect in form or function.

The heat exchanger is rusted, therefore it's imperfect in form.

Maybe the CO is being caused by flame impingement, an overfired gas valve or a blocked chimney but regardless there should never be CO escaping the heat exchanger and venting.  I would just make sure the 8 PPM of CO was not caused by smokers or some other source.

What was the model of the furnace?

[walker]

I did tag it and the customer called Enbridge and they told the customer that I should have never tagged it for anything below 20ppm in the plenum. I found that to be outrageous.

It was on a 7 year old Goodman Mid. Sorry I don't have the M/N with me.

I felt it was not in safe condition to continue operating and tagged it as such.

[Admin]

I doubt that Enbridge told the client that over the phone.  The client should be calling the TSSA not Enbridge.

[walker]

I would hope not.  In my opinion anything over 0 is a hazard.

[Admin]

I found some information about Carbon Monoxide on the Health Canada website - Here

Health Canada's Residential Indoor Air Quality Guidelines

Health Canada has developed an indoor air quality guideline for carbon monoxide in residences. The guideline sets recommended maximum carbon monoxide levels for two types of exposure:
•The short-term limit of 25 parts per million (ppm) based on a one-hour average is meant to prevent the immediate health effects that may occur from exposure to CO for a short period of time (e.g. one hour).
•The long-term exposure limit of 10 parts per million (ppm) based on a 24-hour average protects against health effects that may be caused by repeated exposure to CO over a long period (e,g, over days or weeks).

Health Canada's recommended limits are set to protect people with pre-existing heart problems from extra stress on their heart or lungs due to CO exposure.

The most serious, noticeable symptoms of carbon monoxide poisoning will occur at levels much higher than Health Canada's guidelines.

Carbon monoxide levels in Canadian homes with properly functioning fuel-burning appliances are usually well below the limits recommended by Health Canada.

I found another government of Canada / CMHC article about Carbon Monoxide - Here

(30 ppm) CO detectors are not allowed to sound alarm unless this concentration is maintained for more than 30 days.

[walker]

great I'll have a read over them, thanks

[harshal]

I never found the co on the plenum,though I found in the house a few times.I think the mid and high eff furnace heat exchanger under negative pressure so even if the primary hex is crack u wouldn't found the co in the plenum,but if secondary rotted out e.g.carrier then u may get a little co in the plenum bcoz the return air will be in direct contact with flue above the secondary but that is rare occurrence.

[walker]

well I spoke with my companies head trainer and he states that finding 20ppm is quite normal and nothing to worry about.  They sent another technician back to reevaluate the situation and he removed the tag.  As far as I was concerned in the matter I should not see 13ppm in CO in the plenum of the furnace. I have tested over a 1000 of furnaces and only twice or 3 times have I recorded any CO in the plenum, so I'm not sure where he gets seeing CO in the plenum as being normal.