FAQ - Carbon Monoxide and Stoves

Send any comments to the maintainer Roger Caffin

This note was posted to the news group by our regular American correspondant Ed Huesers, maker of fine igloo-building tools. Since he actually went to the trouble of making real scientific measurements of what levels of carbon monoxide did build up inside an igloo, it seemed useful to report it here. Clearly, there is a lot of myth around. One would think that an igloo would be pretty 'sealed', far more so than a tent. You should also read a report of another experiment which identified one significant source of CO: incomplete combustion with liquid fuel stoves due to faulty (too low) pot stands. This relates to the mention of 'inefficient burning' below.
RNC.

Ed wrote:
Just thought I'd post this in case you wanted to use any of it in your FAQs. We did a carbon monoxide test:

• It was conducted in an igloo measuring 8ft. inside diameter and 60 inches tall with 8 inch thick walls made of packed snow.
• The door extended 12 inches above the floor and we had a nylon poncho doubled up for a door that sealed well and extended below floor level about 6 inches.
• The only ventilation was the 3 inch gap below the hanging poncho and a 1 inch diameter hole in the center of the ceiling.
• Winds were calm to gusting 5mph at 28F.
• With our MSR XGK stove and Coleman fuel the temperatures inside were 48F at the ceiling and 42F 10 inches above the floor. [Freezing point is 32F. RNC]
• The air going out the vent was fluctuating from 1.2 mph to 5 mph depending on the wind outside. We were also on a bit of a ridge top and had eddies with the wind changing directions and could have had varying barometric readings.

Once everything stabilized, we took some readings under various conditions:

• We had readings of 22 ppm of CO 12 inches below the ceiling and 20 ppm 10 inches above the floor.
• When the meter was placed directly in the warm draft of the stove and 36 inches above it, we got a reading of 29 ppm.
• There has been discussion about putting cold snow into a pot without a little water in it so the pot could sweat and drip on the burner and cause inefficient burning of the fuel. We sprinkled ice/snow on the stove until it went out and then relit it and continued to sprinkle smaller amounts. I would consider it to be extreme abuse for any experienced camper. The spattering and all raised the CO by 3 ppm.
• Then just for Eugene we did the cigarette test. With the stove burning and three cigarettes being smoked the reading went to 35 ppm.
• After the smoke cleared (you could have cut it with a knife) and the reading went back down to 24 ppm.
• So we plugged the vent hole. This raised the reading to 35 ppm in 15 minutes before it started stinking so bad that we thought it would be obvious you need a vent.
• We opened the vent, turned off the stove and removed the poncho from the door and within 15 minutes the reading dropped from 35 ppm to 14 ppm.

On previous trips, we have checked CO using a isobutane stove and lantern and haven't had our meter come off the "Low" reading. It changes from low to ppm at 5 ppm.

Here is some text from an OSHA web page:
The Occupational Safety and Health Administration (OSHA) standard for exposure to carbon monoxide prohibits workers' exposure to more than 35 parts of the gas per million parts of air (ppm), averaged over an 8-hour workday. There is also a ceiling limit of 200 ppm (as measured over a 15-minute period).

Here's a link to that page: www.osha-slc.gov/OshDoc/Fact_data/FSNO92-11.html

Ed Huesers
http://www.grandshelters.com