As temperatures records are repeatedly smashed many people in Wales and the wider UK are desperately trying to work out how to keep cool in the sweltering heat.
There is a lot of information circulating on social media with much of it conflicting advice. For example some people say keep your windows open, but if the outdoors is warmer than indoors then all you are doing is making your house hotter.
However one of the worlds most prestigious medical journals, The Lancet, has published a paper offering advice underpinned by science on staying cool. Co-written by professor of heat and health Ollie Jay from the University of Sydney, it goes into great detail about how we need to adapt to our world getting hotter. You can read the full article here but below is the summary of what individuals can do to try and keep cool. Remember that no method is perfect, and each has benefits and limitiations.
Read more: What proof is there that climate change is responsible for our record-breaking temperatures?
Electric fans
Benefits
- Can accelerate convective and evaporative heat losses from the skin resulting in reduced physiological heat strain and improved thermal comfort.
- Up to 50 times lower electricity requirement than air conditioning.
- Simple devices that are more affordable and accessible to many heat-vulnerable people.
- Switching from air conditioning to fans can reduce peak electricity demand and associated risk of power outages during hot weather.
- Require electricity, but battery or solar-powered options available.
Limitations
- Accelerates body heating and worsens physiological heat strain when used at >45°C, most prominently with low humidity.
- Cooling effects of fans diminish with age and other conditions that reduce sweating unless used in conjunction with skin wetting.
- Newly proposed simplified temperature thresholds for safe fan use, irrespective of humidity, are 39°C for healthy adults aged 18–40 years, 38°C for healthy adults aged >65 years, and 37°C for those older adults taking anticholinergic medications.
- High rates of water ingestion needed to offset accelerated dehydration, which can be particularly challenging when fans are used during sleep overnight.
Self-dousing
Benefits
- Applying water to the skin (eg, with a spray bottle or sponge) or donning wet clothing increases evaporative heat loss without additional sweating.
- Reduces physiological heat strain and thermal discomfort. Effective up to at least 47°C.
- Water unsuitable for drinking can potentially be used for sponge dousing.
- Can be used during power outages if water supply available.
Limitations
- Not effective if protective equipment or other clothing requirements restricts evaporation of water directly from the skin.
- Dousing should be repeated regularly (eg, about every 5–10 min) to ensure skin remains wet.
- Sustained supply of water required.
Foot immersion
Benefits
- Immersing feet to above the ankles in cold water promotes conductive heat loss.
- Reduces sweating and improves thermal comfort.
- Suitable for use during power outages if water supply available.
Limitations
- Has not been shown to reduce physiological heat strain.
- Very cold water (<5°C) can induce intense local thermal discomfort.
- Increased risk of slips and falls.
Misting fans
Benefits
- Electric fans that emit high-pressure water spray can enhance evaporative heat loss from the skin without additional sweating.
- Reduces physiological heat strain and thermal discomfort.
- Can reduce air temperature immediately around a person by extracting latent heat energy from the air, especially in arid climates, and from hot surrounding surfaces.
Limitations
- Not suitable for most indoor applications, unless spray volume is reduced.
- If area of use is not well ventilated, increases in humidity reduce cooling effectiveness.
- Increased risk of slips and falls.
- Clean water and electricity supply required.
- Restricted cooling range (within about 2–3 m).
Evaporative coolers
Benefits
- Forcing air across a wet membrane reduces air temperature by extracting latent energy.
- Air temperature reductions of up to 10–15°C possible in arid climates.
Limitations
- Minimal cooling effect in humid climates.
- High capital costs.
- Without maintenance can become mosquito breeding sites.
Ice towels
Benefits
- Crushed ice wrapped in a damp towel applied to the neck and chest increases heat loss via conduction. Damp chilled towels temporarily draped over the head and lap also augment evaporative heat loss.
- Short (1–2 min), repeated (about every 10 min) application can reduce physiological heat strain and thermal discomfort.
Limitations
- Preparation is labour and time intensive.
- Depending on conditions, can melt and become ineffective within approximately 30 min.
- Ice supply required.
- Low portability.
Drink cold water
Benefits
- Provides internal conductive heat transfer between hot body and cool ingested fluid.
- Can prolong exercise in hot and humid climates.
Limitations
- Internal cooling effect can be offset by parallel reductions in sweating.
- If ingested after sweating starts, negligible effect on core temperature.
- Drinking very cold water might decrease the amount of fluids ingested.
Reducing activity
Benefits
- Breaks in physical activity >5–10 min reduces metabolic heat production sufficiently to lower body temperature.
Limitations
- Breaks must be compatible with productivity goals in occupational settings.
- Benefits limited if other cooling behaviours are not permitted (eg, shade and removing clothing).
Optimising or removing clothing
Benefits
- Removing or modifying clothing or protective equipment reduces resistance to sweat evaporation and convective heat exchange at skin surface.
- Strategically placed vents can assist sweat evaporation.
Limitations
- Can compromise safety if clothing or equipment serve protective function.
- Clothing ensemble should be easily modifiable.
- Can compromise skin protection from ultraviolet radiation.
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