1. What is humidity?
Humidity is the amount of water vapor (dampness) in the air at any given time. There are three main measurements of humidity: absolute humidity, relative humidity, and specific humidity. For the purposes of this article, we’re going to focus on relative humidity.
2. What is relative humidity?
Relative humidity, which is usually expressed as a percentage, depends on temperature. It refers to the absolute humidity at a given moment relative to a maximum humidity given the same temperature.
Relative humidity is an important metric in weather forecasts because it is an indicator of the likelihood of precipitation, dew, or fog.
3. What is a comfortable humidity level?
Humidity is a factor in thermal comfort. Meaning, high or low relative humidity can be uncomfortable.
According to the Environmental Protection Agency, indoor relative humidity should be kept below 60%. Ideally, between 30% and 50%.
The DOH states that “for thermal comfort, the optimum range for relative humidity is 40 to 60 percent in the summer and 30 to 50 percent in the winter.”
4. What happens if humidity levels are high?
High relative humidity reduces people’s ability to lose heat through perspiration and evaporation.
In other words, the human body uses perspiration as a way to self-regulate its temperature. If the air is damp, it takes longer for perspiration to evaporate. So, as humans perceive the rate of heat transfer from the body rather than temperature itself, when the relative humidity is high we feel warmer. The effect is similar to raising the temperature.
In fact, the level of relative humidity directly affects the temperature ranges found to be acceptable by humans.
From a health standpoint, some people might experience difficulty breathing in humid environments. They will often hyperventilate in response, causing sensations of numbness and faintness, among others.
Humidity levels above 60% can also create a moist environment where microbial life like bacteria, fungi, mold, and dust mites thrive.
5. What happens if humidity levels are low?
Low relative humidity levels (below 30 percent) can cause excessive thirst and dry skin, lips, and eyes. It has also been associated with eye irritation and nosebleeds, since it may cause the tissue lining the nasal passages to dry and crack.
Very low humidity can create discomfort, respiratory problems, and aggravate allergies in some people.
You can usually feel the effect of low humidity on airplanes, where humidity levels are usually below 20%. In that situation, the World Health Organization advises to:
- Use skin moisturizing lotion or a saline nasal spray to moisturize the nasal passages.
- Wear eyeglasses instead of contact lenses to prevent discomfort to the eyes.
- Limit the consumption of caffeine and alcohol during long flights because of its diuretic effect.
6. How to measure humidity levels
With a specialized instrument
Hygrometer. That’s the name of the instrument used to measure the levels of humidity in the air.
You can buy one online for less than 30 dollars. They usually gauge both humidity and temperature.
Without a hygrometer
There are a few ways to deduce if humidity levels are high or low without a specialized instrument:
- Thermal discomfort. If you feel too hot when the temperature does not warrant it, humidity levels might be too high. In the same vein, if your skin, eyes, or nasal passages get dry and crack, humidity levels might be too low.
- Condensation. It can be a sign of high humidity. Condensation may form when warm humid air contacts a cold surface.
- Mold. Dampness in the air can supply enough moisture for mold growth. Also fungi and dust mites.
- Static electricity. If you notice that your clothes cling or that dust particles stick to electrically-charged surfaces, it may be a consequence of low humidity levels.
7. How to control humidity levels
Humidity levels can rise in a building as a result of:
- Steam radiators.
- Moisture-generating appliances such as dryers.
- Combustion appliances such as stoves.
A proper heating, ventilation and air conditioning (HVAC) system will help in keeping humidity levels within the 30% to 50% range.
If an HVAC system is not in place, or not enough to combat high humidity levels, then a dehumidifier may help.
When placed in a room, a dehumidifier will suck in air, take the moisture out of it, and then blow the air back out. The excess moisture then drips into a collection tank which will have to be emptied from time to time.
There’s a wide variety of dehumidifiers in the market. Their price is usually proportional to the size of the area they can cover (in square or cubic feet) and the capacity of their collection tank.
If, on the contrary, it is low levels of humidity you’re looking to combat, then a humidifier may help instead.
A humidifier works by releasing water vapor into the air. To do so, you will have to previously fill its tank with water.
Same as with the dehumidifiers, there’s a wide variety of humidifiers in the market and their price is usually proportional to their size and capacity.