It is important to separate two concepts that are often confused from the start. Heat stress<\/strong> is the heat load to which the worker is exposed; thermal overload<\/strong> is the body’s response to that load. One is the cause, the other the effect. Occupational risk prevention works on the first to avoid the second. <\/p>\n There are two types of heat stress, and although heat stress is the most common in Spain, both are recognized occupational hazards.<\/p>\n Heat stress<\/strong> occurs when the body cannot dissipate the heat generated by physical activity combined with heat absorbed from the environment. Sweating and vasodilation are no longer sufficient, body temperature rises, and dehydration, cramps, fatigue, and, in severe cases, heat stroke appear. It is the typical risk in construction, agriculture, and, inside facilities, in machining, welding, or foundry workshops, where machinery adds heat to what is already present outside. <\/p>\n Cold stress<\/strong> is the opposite: the body loses heat faster than it can generate it. It causes shivering, loss of sensation in the extremities, and, in extreme exposures, hypothermia or frostbite. It affects work in cold storage rooms, refrigerated warehouses, and outdoor activities in winter. <\/p>\n Heat stress almost never has a single origin. It is produced by the combination of four factors that reinforce each other. <\/p>\n Understanding that there are four levers, and not just “it’s hot,” is what allows you to attack the problem from several fronts at once instead of relying on a single measure.<\/p>\n The effects of heat stress range from mild discomfort to medical emergencies, and knowing how to recognize the early signs is what prevents reaching the severe ones.<\/p>\n The first symptoms of heat stress are excessive sweating, intense thirst, fatigue, headache, dizziness, and loss of concentration. The latter is especially dangerous in environments with machinery: a worker who loses focus due to heat not only performs worse, but makes more mistakes and has more accidents. Muscle cramps, especially in the legs and abdomen, are another common warning that the body is losing salts through sweat. <\/p>\n Heat stroke occurs when body temperature exceeds 40\u00b0C and the body can no longer cool itself. Signs include confusion, hot and dry skin (stops sweating), loss of consciousness, and seizures. It is a medical emergency that can be fatal and requires immediate action. It is not a theoretical risk: heat waves cause work-related deaths in Spain every summer, which is why monitoring is mandatory during critical months. <\/p>\n Heat stress is not only a health problem, it is a bottom-line problem. Above a certain temperature, worker performance drops measurably: concentration decreases, pace slows, and errors and unscheduled breaks increase. <\/p>\n In a machining or welding workshop, this translates into poorly executed parts, extended deadlines, and workers who by mid-afternoon no longer perform the same. This is why many industrial companies that start looking for “how to comply with regulations” end up discovering that cooling workstations pays for itself with recovered productivity. The heat suffered by the worker and the production lost by the company are two sides of the same problem. <\/p>\n In Spain, protection against heat stress is a legal obligation of the employer, not a recommendation. Royal Decree 486\/1997<\/strong> on workplaces sets temperature ranges for work in enclosed spaces: between 17 and 27\u00b0C for sedentary work (offices) and between 14 and 25\u00b0C for light work. The following table summarizes the most commonly used references. <\/p>\n Royal Decree-Law 4\/2023<\/strong> reinforced these obligations after several heat-related deaths: it requires adapting or reducing working hours when the State Meteorological Agency issues warnings for extreme temperatures and the risk cannot be controlled by other measures. This is complemented by the National Plan for preventive actions during high temperatures<\/strong>, active from May to September, and the technical guides of the National Institute for Occupational Safety and Health (INSST)<\/strong>. Risk assessment for heat stress, worker information, and preventive measures are mandatory and their absence is subject to penalties. <\/p>\n <\/p>\n Effective prevention of heat stress combines organizational and technical measures. The former are inexpensive and immediately applicable; the latter address the root of the problem. <\/p>\n Organizational measures help, but when heat is structural (a workshop where machinery raises the temperature every day) you need to lower the temperature of the work environment. This is where many prevention guides fall short: they recommend “installing air conditioning” without explaining that cooling an entire facility with high ceilings and open doors is usually unfeasible or extremely expensive. <\/p>\n The realistic alternative is to cool the workstation, not the building. A portable industrial air conditioner directs cold air directly to the worker without construction or installation, works in environments up to 45\u00b0C, and solves the critical point (the person) without the cost of cooling thousands of cubic meters. Depending on the type of space, an evaporative cooler or high-volume fans may be even more efficient in consumption. The key is to size correctly and choose the right technology for each facility. <\/p>\nHeat stress and cold stress: they are not the same<\/h2>\n
![\"heat](\"https:\/\/blizzcool.es\/wp-content\/uploads\/2026\/07\/combatiendo-estres-termico-en-nave-industrial-1024x572.png\")
<\/p>\nWhy heat stress occurs: the four causes<\/h2>\n
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Symptoms and effects on worker health<\/h2>\n
Early warning signs not to ignore<\/h3>\n
Heat stroke: when it becomes an emergency<\/h3>\n
The invisible cost: how heat undermines productivity<\/h2>\n
What Spanish regulations say about high temperatures<\/h2>\n
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\n \nType of work<\/th>\n Recommended temperature<\/th>\n<\/tr>\n<\/thead>\n \n Sedentary work (office)<\/td>\n 17 \u2013 27\u00b0C<\/td>\n<\/tr>\n \n Light work<\/td>\n 14 \u2013 25\u00b0C<\/td>\n<\/tr>\n \n Moderate or heavy work<\/td>\n No limit set by RD; specific risk assessment required<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n ![\"portable](\"https:\/\/blizzcool.es\/wp-content\/uploads\/2026\/07\/aire-portatil-para-reducir-estres-termico-1024x576.png\")
<\/p>\nHow to prevent heat stress at work<\/h2>\n
Organizational measures<\/h3>\n
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Technical measures: cool where the worker is<\/h3>\n
Cool where your workers are, not the entire facility<\/h2>\n