Out of the dark

摘要

The ability to access a reliable source of light in the field, or at times of accident or emergency, enables markers to be laid and signals to be sent. It can make the difference between rescue and jeopardy, safety or disaster.rnDelivering light reliably and safely in difficult, extreme or hazardous conditions, though, restricts the type of illumination that can be used. Flares or other pyrotechnics bring with them the risk of fire, particularly in accident zones where flammable gases or liquids may be present. Electric torches may also risk a spark and, being powered by batteries, may prove unreliable if in use for too long. Candles have the risk of an open flame, and cannot be used in adverse weather.