Carbon monoxide (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 onΒ 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 CO concentration from reaching dangerous levels; safety can be enhanced by the use of small portable CO detectors.

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
– Dehydration (stay well hydrated) – Snow holes tend to be worse than tents (beware of all of the
– Hyperventilation (more exposure to CO)
– High altitude
– Tent icing and snow cover (makes tent less porous — keep cleaned to allow air flow)

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