EXPLAINERWhile AC keeps us cool, it can also cause dry skin and irritation. Here are some tips to keep comfortable this summer.Summer is here and temperatures are rising across the Northern Hemisphere, where nearly 90 percent of the world’s people live. The heat is pushing people to rely on air conditioners to stay comfortable.While air conditioners provide relief from extreme heat, they also remove moisture from the air, which can cause skin dryness and irritation.In this visual explainer, Al Jazeera breaks down how air conditioners work, what they can do to your health and practical tips to protect yourself while you stay cool.How does an air conditioner work?Air conditioners work by removing heat and moisture from indoor air and releasing it outside.The process starts when the indoor unit pulls in warm air and sends it over cold evaporator coils. Inside the coils, liquid refrigerant absorbs the heat, evaporates into a gas and cools the air. A fan then blows the cooled air back into the room.The now-warm refrigerant gas travels to an outdoor unit, which releases the heat through a condenser coil that turns it back into a liquid.The liquid refrigerant returns indoors to repeat the cycle.(Al Jazeera)When was AC invented?The invention of modern air conditioning is generally credited to the American engineer Willis Carrier, who in 1902 designed a humidity-control system for a New York printing plant using chilled coils.Window-mounted units followed in 1931, and after World War II, mass production brought AC into homes and offices.An air conditioner is mounted in the window of an office, circa 1955 [File: Lambert/Getty Images]By the 1990s, growing environmental concerns led to the phaseout of ozone-depleting chlorofluorocarbons, or CFCs, in favour of hydrofluorocarbons (HFCs).In the 2010s, newer refrigerants, such as R-32 and R-290 (propane), marked a shift towards lower-emissions cooling.Where is air conditioning needed most?As temperatures rise, more countries around the world are increasingly adopting air conditioners. Without effective or accessible cooling, many people may be exposed to heat stress and related illnesses.According to the World Health Organization, heat stress is the leading cause of weather-related deaths and can exacerbate underlying illnesses, including cardiovascular disease, diabetes, mental health issues and asthma, as well as increase the risk of accidents and the transmission of a number of infectious diseases.The regions with the highest heat stress are generally those that have a combination of high temperatures, high humidity and intense sun exposure.(Al Jazeera)Heatstroke is the most extreme form of heat stress – a severe medical condition that occurs when a body’s internal temperature exceeds 40 degrees Celsius (104 degrees Fahrenheit) – and can be life-threatening if not treated immediately.The graphic and list below summarise 10 tips to help minimise the risk of heatstroke: