An FCC-licensed radio service that allows long-distance communication when cell service and the internet fail. See ch. 19.
Haybox cooker (retained-heat cooking)
A pot that is boiled for a few minutes and then well insulated so it finishes cooking on its own heat. It saves a lot of fuel. See ch. 22.
Heat exhaustion
The stage before heat stroke: cool, pale, clammy skin, heavy sweating, dizziness, nausea. If you are unsure whether it is this or heat stroke, treat it as heat stroke. See chs. 7 and 10.
Heat index
The temperature the body "feels" when heat and humidity combine. In direct sun it can be up to 15 °F (8 °C) higher than the value in the shade. See ch. 10.
Heat stroke
Emergency: body temperature above 103 °F (39.4 °C), hot skin, confusion. Call 911 and cool the person immediately with cold water. See chs. 7 and 10.
HELP position
A posture for losing less heat while floating in cold water with a life jacket: arms crossed over the chest, knees up, legs together. The letters stand for Heat Escape Lessening Posture. Seech. 13.
HEPA filter
A high-efficiency air filter that traps very fine particles, including most biological agents. It does not stop gases. See chs. 16 and 21.
Hollow-fiber filter
A portable water filter that removes bacteria and parasites, not viruses or chemicals. If it freezes it can crack without you noticing. See ch. 3.
HVAC
A building's heating, ventilation, and air conditioning system. In a chemical leak or radioactive fallout it is turned off so it does not draw in outside air. See chs. 16 and 18.
Hypothermia
A dangerous drop in body temperature. Signs: shivering, clumsiness, confusion, slurred speech. It can happen at 50 °F (10 °C) with wet clothes and wind. If the person stops shivering and is confused, it is serious. See chs. 7 and 14.
