see also:

• keeping warm when camping or hiking
• better sleeping when camping - sleep naked or not?
• how to sleep comfortably and healthier at 7deg C without a sleeping bag

• most healthy young adults can tolerate reasonably cold air whilst camping as long as it isn't cold enough to cause frostbite or hypothermia
• older campers with heart failure run the risk of developing sudden onset of potentially fatal pulmonary oedema due to the blood vessels in their skin constricting with resultant effective fluid overload centrally
• others with poor circulation such as older smokers (but also including those with Raynaud's phenomenon) may be particularly susceptible to very cold, blue or pale, hands and feet with risk of frostbite
• inhaling moderately cold air below 10degC down to zero deg C may cause significant issues with many people camping:
  • cold discomfort impacting sleep
  • runny noses or blocked noses and snoring with disturbed sleep, sore dry throat from mouth breathing and increased risk of cold dry air reaching the lungs
  • dried out mucosal membranes (cold air carries much less water vapour) resulting in blood noses (epistaxes) especially if one is on blood thinners including aspirin or have chronic sinusitis or have high blood pressure (unfortunately heating this cold air without humidification can further dry out the mucosa)
  • inflamed reddened exposed nasal skin
  • cold-induced bronchospasm causing an asthma attack, croupy-cough or just dry incessant coughing
    • cold air is dry as well as cold and can cause the airways to constrict or become inflamed an can trigger the cough reflex as well as making respiratory conditions worse such as croup, asthma, pneumonia, influenza, Covid-19
    • smoke from a camp fire is also going to make this worse!
  • increased risk of succumbing to a carried viral or bacterial load and developing a cold or worse
  • a 2024 study showed lower air temperature exposure was associated with an increased risk of heart attacks two to six days after cold air exposures ³⁾
  • WHO recommends houses should be designed to have minimum overnight temperatures of 18degC as lower temperatures are associated with increased health risks
• tolerance to cold air breathing is probably determined by a number of factors:
  • nose shape
    • a 2023 genomic study showed that those with longer noses with better capacity for warming and humidification of inhaled air was probably inherited from Neanderthals (particularly genome region ATF3), presumably as this helped Neanderthals adapt to colder European climates
  • mouth breathing instead of nose breathing impairs warming and humidification of inhaled air causing dry sore throats and potential respiratory symptoms
  • asthma tendency

• air temperature inside your tent can be increased substantively by:
  • ensuring you have a small tent (eg full fabric 2P dome tent, preferably inside a larger tent which can reduce wind chill even further and reduce dew forming) or swag under a tarp, and,
  • use your body to heat the air (use a quilt to allow body heat to escape into the air rather than a sleeping bag), and
  • use an adjunct to keep your body warm and also heat the air such as an electric blanket or car seat heated cushion
  • if you have plenty of 12V battery power, use a 12V 150W car demister heater intermittently to rapidly warm the air
  • consider insulation over your inner tent
  • consider sleeping on a stretcher to raise you up to a warmer air temperature in the tent
  • MAKE SURE you have a well insulated sleeping pad/mattress - the higher R rating the better - eg. 7-15cm memory foam self-inflating mattresses will usually have R values over 8 - an air mattress without insulation is NOT a good option - you will be very cold!
  • sleeping semi-naked will allow your body heat (50-100W) to add to the air warmth provided by the electric blanket
    • most will find it comfortable to be semi-naked with an air temp of over 13degC if they are lying on an electric blanket running at around 20W (higher if air temperatures are lower)
  • see keeping warm when camping or hiking
• option 1: keeping the inner tent air tight:
  • will allow the heated air to be retained inside the tent,
  • will reduce cold air entry into the tent,
  • will allow the moist expired air from your breathing to be retained and not cause dried out mucosa (the warming of the air should stop this condensing inside your tent which is a reason one usually has ventilation in a tent),
  • will avoid any wind chill effects
  • will not cause you to build up excessive carbon dioxide or run out of oxygen (you will adequately refresh the air when you open the tent to get out every 12hrs)
  • you will not run out of oxygen or get too much carbon dioxide build up in just one night of 1 person sleeping in a 2P sealed dome tent (ensure you refresh the air during the day)
  • you may have to manage condensation - so this option will not work well with a swag or when there are high humidity levels
  • without any heating you will only get air temperatures 2-3degC above outside temperatures, while an electric blanket on low setting of ~20W may give you 4-5degC above outside temperatures
  • does not require as much power to keep warm as does the open door option 2.
  • if you run an electric blanket at 48W, you can get tent temperatures of 15degC while outdoor is 7degC
• option 2: electric blanket + open door
  • the aim here is to use the electric blanket to create a heated air wall adjacent to the door to minimise ingress of cold air similar to what is used at entrances to department stores
  • as long as the open door is protected from wind and you have an electric blanket which can heat the air adjacent to the 2P dome tent open door, you can raise tent air temp from 7degC outside temp to 13degC at 8“ below ceiling of tent and perhaps 12” inside the open tent door!
  • this will consume at least 48W of power but does allow better connection with nature, a rapid escape route without need to find those zips, and allows any flatus to escape!
  • if the outside temp drops you can either:
    • reduce the amount of cold air coming in by closing the door with mesh or fabric
    • increase the electric blanket heat output if you have plenty of battery capacity
  • optionally retain heat more by:
    • having the 2P dome tent without fly inside a 4P tent which has minimal wind breeze (it is important to block wind from entering the 4P tent otherwise it may bounce backwards off the walls and into your 2P tent
    • then add an insulating blanket on top of the dome tent
  • Warnings:
    • don't sleep with open door without insect protection if it is mosquito season!
    • don't have an open door with food smells in your tent otherwise you will have possums, etc enter your tent
    • you may need to wake before sunrise to close the door for privacy if sleeping naked in which case you revert to option 1.
• option 3: use a diesel air heater
  • these are not commonly used by tent campers but are popular with those sleeping in caravans although even with muffler silencers, they can be noisy (~75dB) and annoy other campers
  • they should be placed outside the tent (so you don't get carbon monoxide poisoning - the silent camp killer) with the warm air duct flowing into the tent
  • requires some 12V power most run at ~42W which is similar to an electric blanket on full (you will also need a 12V DC-DC voltage regulator as many of these do not accept 13.8V from a lithium battery, and for start up they will need 15A current so a standard cig lighter will not suffice) plus diesel fuel at 0.16-0.48L/Hr thus 10L tank will last at least 20hrs and will weigh 7-10kg plus fuel
• option 4: get a powered site and use a 240V electric heater
  • this is the most effective option but uses a lot of power - over 1000W - but this can heat larger tents or caravans all night long - if you have the power supply
  • need to ensure it cannot fall over or have flammable materials fall onto it
  • NB. a 100AH 12V lithium battery can only give you 1200W for 1hr (via an AC inverter) - hence you need a powered site with 240V to run such heaters