--- title: "Heat Stress and Hydration Glossary: 40 Terms for Crews" description: "Plain-English definitions of 40 heat stress, hydration and OSHA terms for crews, from acclimatization to WBGT, each with its source." url: https://jmarsolutions.multisites.ai/glossary publisher: JMAR Solutions phone: +1-214-632-7780 quote: https://jmarsolutions.multisites.ai/contact --- # Heat stress and hydration glossary 40 terms crews and safety managers use, in plain English. Every fact links to its source. Search the glossary No terms match. Try a shorter word. ## A [Acclimatization](https://jmarsolutions.multisites.ai/glossary/acclimatization) Acclimatization is the body's gradual adaptation to heat, such as sweating more efficiently. NIOSH says to build work time in the heat over 7 to 14 days. ## B [Buddy system](https://jmarsolutions.multisites.ai/glossary/buddy-system) A buddy system pairs workers so each watches the other for signs of heat illness, such as confusion, heavy sweating or dizziness, and speaks up fast. ## C [cGMP](https://jmarsolutions.multisites.ai/glossary/cgmp) cGMP means current good manufacturing practice, quality rules that FDA enforces to control how products are made. JMAR lists "cGMP Certified" on its quality line. [Cold stress](https://jmarsolutions.multisites.ai/glossary/cold-stress) Cold stress is the strain on workers in cold places, when heat leaves the body faster than it can be replaced. It can lead to hypothermia and frostbite. [Core body temperature](https://jmarsolutions.multisites.ai/glossary/core-body-temperature) Core body temperature is the temperature deep inside the body. Heat stroke is a core temperature emergency: it can pass 106°F within 10 to 15 minutes. ## D [Dehydration](https://jmarsolutions.multisites.ai/glossary/dehydration) Dehydration is a condition caused by losing too much fluid from the body. It happens when you lose more fluid than you take in, such as through heavy sweating. ## E [Electrolyte](https://jmarsolutions.multisites.ai/glossary/electrolyte) Electrolytes are minerals with an electrical charge when dissolved in water or body fluids. Sodium, potassium, magnesium and chloride are common ones that sweat removes. [Electrolyte powder packet](https://jmarsolutions.multisites.ai/glossary/electrolyte-powder-packet) An electrolyte powder packet is a dry mix of minerals, often with sugar and flavor, that you stir into water. It is a common format for crews and teams. ## F [Frostbite](https://jmarsolutions.multisites.ai/glossary/frostbite) Frostbite is an injury to the body caused by freezing. It is one of the cold-related illnesses workers face in very cold weather or in unheated work areas. ## G [General Duty Clause](https://jmarsolutions.multisites.ai/glossary/general-duty-clause) The General Duty Clause is Section 5(a)(1) of the OSH Act. It requires employers to keep workplaces free from recognized hazards likely to cause death or serious harm. ## H [Heat cramps](https://jmarsolutions.multisites.ai/glossary/heat-cramps) Heat cramps are painful muscle cramps or spasms in the abdomen, arms or legs. They hit workers who sweat heavily during hard work and can signal heat exhaustion. [Heat exhaustion](https://jmarsolutions.multisites.ai/glossary/heat-exhaustion) Heat exhaustion is the body's response to losing too much water and salt, usually through heavy sweating. Signs include headache, nausea, dizziness, weakness and heavy sweating. [Heat illness prevention plan](https://jmarsolutions.multisites.ai/glossary/heat-illness-prevention-plan) A heat illness prevention plan is a written employer plan to find heat hazards, control them, train workers, name who supervises daily, and respond fast to illness. [Heat index](https://jmarsolutions.multisites.ai/glossary/heat-index) The heat index measures how hot it feels when humidity is added to the actual air temperature. It assumes shade and light wind, so full sun makes the real risk higher. [Heat index work rest chart](https://jmarsolutions.multisites.ai/glossary/heat-index-work-rest-chart) A heat index work/rest chart links the heat index to how long crews can work and how long they should rest. Charts differ, so use the one your safety program adopts. [Heat rash](https://jmarsolutions.multisites.ai/glossary/heat-rash) Heat rash is a skin irritation from heavy sweating in hot, humid weather. It shows as red clusters of pimples or small blisters, often on the neck, chest and elbow creases. [Heat stress](https://jmarsolutions.multisites.ai/glossary/heat-stress) Heat stress is the total heat load on a worker's body from hard work, hot air and sun, and clothing or gear. When the body cannot shed that heat, illness can follow. [Heat stroke](https://jmarsolutions.multisites.ai/glossary/heat-stroke) Heat stroke is the most serious heat-related illness. The body can no longer control its temperature, and the worker needs emergency care. Call 911. [HeatRisk](https://jmarsolutions.multisites.ai/glossary/heatrisk) HeatRisk is a National Weather Service forecast that gives a color and number for heat concern at a location, up to seven days ahead, with advice on who is most at risk. [Hydration](https://jmarsolutions.multisites.ai/glossary/hydration) Hydration is keeping enough fluid and electrolytes in the body to work well. For crews in the heat, it means steady drinking all shift, not only when thirsty. [Hyponatremia](https://jmarsolutions.multisites.ai/glossary/hyponatremia) Hyponatremia is low blood sodium: a sodium level lower than normal. It can follow long sweating when a person drinks lots of plain water without replacing salts. [Hypothermia](https://jmarsolutions.multisites.ai/glossary/hypothermia) Hypothermia is abnormally low body temperature. A body temperature that is too low affects the brain and makes a person unable to think clearly or move well. ## L [Liquid electrolyte concentrate](https://jmarsolutions.multisites.ai/glossary/liquid-electrolyte-concentrate) A liquid electrolyte concentrate is a small-volume liquid of dissolved minerals that you add to a drink. There is no powder to mix, and a bottle holds many servings. ## M [Magnesium](https://jmarsolutions.multisites.ai/glossary/magnesium) Magnesium is a mineral that helps more than 300 enzyme systems in the body, including those for muscle and nerve function. It is also an electrolyte. ## N [NIOSH](https://jmarsolutions.multisites.ai/glossary/niosh) NIOSH, the National Institute for Occupational Safety and Health, is the federal institute that researches work injury and illness and makes recommendations to prevent them. It is part of CDC. ## O [On-site consultation](https://jmarsolutions.multisites.ai/glossary/on-site-consultation) OSHA's On-Site Consultation Program gives small and medium-sized businesses free, confidential help with workplace safety. It can help employers plan for heat-related illness and injury. [Oral rehydration solution](https://jmarsolutions.multisites.ai/glossary/oral-rehydration-solution) Oral rehydration solution (ORS) is a mix of clean water, salt and sugar. Doctors use it to replace water and electrolytes lost in illnesses such as diarrhea. [OSHA heat NEP](https://jmarsolutions.multisites.ai/glossary/osha-heat-nep) The OSHA Heat National Emphasis Program is an enforcement and outreach effort aimed at heat hazards in high-risk industries. OSHA revised it on April 10, 2026. [OSHA heat rule](https://jmarsolutions.multisites.ai/glossary/osha-heat-rule) The OSHA heat rule is a proposed federal standard, Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings. As of November 2026 it is not final. ## P [Potassium](https://jmarsolutions.multisites.ai/glossary/potassium) Potassium is an electrolyte found in all body tissues. It helps cells, the heart and muscles work properly and helps keep fluid inside cells. ## R [Rhabdomyolysis](https://jmarsolutions.multisites.ai/glossary/rhabdomyolysis) Rhabdomyolysis, or rhabdo, is a medical condition tied to heat stress and long physical exertion. Muscle tissue breaks down and can harm the kidneys and heart. ## S [Single-serve pack](https://jmarsolutions.multisites.ai/glossary/single-serve-pack) A single-serve pack is a small packet with one portion of electrolyte liquid. JMAR sells Rapid Restoration Drops single serves in 15, 50 and 350 counts. [Sodium](https://jmarsolutions.multisites.ai/glossary/sodium) Sodium is the main electrolyte in sweat. It helps control the amount of fluid in your body and helps nerves and muscles work properly. [Sports drink](https://jmarsolutions.multisites.ai/glossary/sports-drink) A sports drink is a flavored drink with water, electrolytes and usually sugar. NIOSH names sports drinks with balanced electrolytes for long, sweaty work in the heat. [Sweat rate](https://jmarsolutions.multisites.ai/glossary/sweat-rate) Sweat rate is how much sweat a person loses over time. It changes with heat, humidity, effort, clothing and fitness, so it differs from worker to worker. ## T [Texas HB 2127](https://jmarsolutions.multisites.ai/glossary/texas-hb-2127) Texas HB 2127 is a 2023 state law that overrides certain local rules. It ended the Austin and Dallas ordinances that required water breaks for construction workers. [Toolbox talk](https://jmarsolutions.multisites.ai/glossary/toolbox-talk) A toolbox talk is a short safety briefing held on the jobsite before or during work. For heat, it reviews signs of illness, water, breaks and what to do in an emergency. ## W [Water rest shade](https://jmarsolutions.multisites.ai/glossary/water-rest-shade) Water. Rest. Shade. is OSHA's heat safety message: cool water to drink, scheduled rest breaks, and a cool place to recover. OSHA encourages all three for prevention. [WBGT](https://jmarsolutions.multisites.ai/glossary/wbgt) Wet bulb globe temperature (WBGT) combines temperature, humidity, sunlight and air movement into one heat stress reading. OSHA uses it to decide if a heat hazard existed. [Work/rest schedule](https://jmarsolutions.multisites.ai/glossary/work-rest-schedule) A work/rest schedule sets how long crews work in the heat and how long they rest in a cool place. Rest gets longer as heat, sun and workload rise. ![Ironworkers silhouetted on a steel frame against a hot orange sunset](https://jmarsolutions.multisites.ai/_astro/sunset-steel.IhAMDca0_6wk53.webp) ## See it on your crew in 15 minutes Jennifer walks your safety team through the drops, the protocol and the numbers on a short live call. [Book a 15-minute demo](https://calendly.com/jen-jmarsolutions/15-min-meeting)