Vent that tent!
Jan 21, 2005 16: 41 EST
From a recent issue of Wilderness and Environmental Medicine, some very important information for avoiding deadly carbon monoxide (CO) poisoning in tents. The following are excerpts from the article, with reference for more information at the conclusion:
Case reports verify that CO poisoning within tents and snow caves is a real and probably overlooked problem. It is potentially an even greater problem at altitude because of the multiplicity of risk factors for CO toxicity. Despite multiple anecdotal reports of climbers perishing from CO poisoning on Himalayan peaks circulating in climbing circles, the danger does not appear to be widely recognized.
Diagnosing CO poisoning in the early stages may be difficult because of the nonspecific nature of symptoms and (at altitude) their similarity to AMS. The masking of symptoms when subjects are sedentary exacerbates the problem, and these are likely to be the occasions when individuals are subjected to the highest CO levels, such as resting and cooking in tents for hours during inclement weather. All attempts must be made to prevent COHb concentration reaching dangerous levels. Some of the evidence on how to do this is well founded; some is fairly poor. Opportunities for research in this interesting and very relevant area are abundant.
Safety could be enhanced by the use of small portable CO detectors. We hope to see no more case reports of healthy, fit young people dying from an entirely preventable cause.
Summary of risk factors (and proposed precautions) for carbon monoxide poisoning in tents:
-- Cooking (Avoid prolonged simmering, keep stove highly pressurized, use white pure fuels, use small diameter pans, use maximal blue flame and avoid low flames)
-- Yellow flame (Turn stove off, repressurize, relight, maximize tent ventilation for a few minutes)
-- Inadequate tent ventilation (Ventilation area at least 50cm2, CO egress port as high as possible, O2 ingress port as low as possible, higher risk in zero wind conditions)
-- Insidious onset of symptoms if sedentary (beware headache and fast heart rate, make regular trips outside to unmask symptoms, ventilate tent at regular intervals, ventilation does not have to be continuous)
-- Dehydration (stay well hydrated)
-- Snow holes tend to be worse than tents (beware of all of the above)
-- Hyperventilation (more exposure to CO)
-- High altitude
-- Tent icing and snow cover (makes tent less porous -- keep cleaned to allow air flow)
For more information, read the entire article:
Carbon Monoxide Poisoning in Tents—A Review
Simon Leigh-Smith, MBChB, MRCGP, FRCSEd (A&E)Wilderness and Environmental Medicine: Vol. 15, No. 3, pp. 157–163.
Image of "safe" cooking tent with tarp between tents at high camp on Everest courtesy of Pemba Sherpa, 2004.
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