Absolute Humidity: Definition, Causes & Effects

Our air is enriched with water: more precisely, with water vapor. This water vapor is always present, but it fluctuates depending on temperature and becomes more or less noticeable as a result. When the air is warmer, it can absorb or hold more water. We notice this, for example, in muggy summer weather or during tropical rain, which brings larger drops and more water with it. When the air is cold, on the other hand, it absorbs less water. That's why we notice dry air on cold winter days. This phenomenon is especially apparent for glasses wearers: coming from cold temperatures into a warm room causes their lenses to fog up.

Absolute Humidity (φ): Causes & Formation

The absolute humidity (φ) describes water vapor density: that is, the total amount of water contained within a given volume of air. Absolute humidity is expressed in grams, whereas relative humidity is expressed as a percentage.

The relative humidity (p) depends heavily on temperature: air at 30 °C can hold 31 grams of water per cubic meter (31 g / m³), while air at 5 °C can only hold 7 grams of water per cubic meter (7 g / m³). The result at cold temperatures: condensation or dew forms, since the air can't absorb as many water molecules. So if you often find water droplets on your bedroom window in winter, you should ventilate more frequently and raise the temperature slightly.

So how does water vapor increasingly get into our rooms? Quite simply: through our breathing. We release moisture into our surroundings with every exhale. The more people in a room, the more water vapor rises in the indoor air. But plants also release water, and moisture is generated when showering, drying laundry, or cooking, which enriches the surrounding air. The only remedy here is an air exchange – ideally through burst ventilation.

Due to their surface properties, some building materials absorb more moisture than others: for example, untreated wood, limestone, plaster, or brick. Materials like paper or textiles also store moisture over a long period and release it again when humidity is low, for example books, upholstered furniture, curtains, or carpets.

Many new buildings aren't yet fully dried out. The moisture contained in the building materials is then released into the surrounding air, including into the interior of the room. To prevent health problems or mold in these cases, you should ventilate more frequently – ideally throughout an entire heating season.

Stay well informed, for your healthy life

Health Effects of the Absolute Humidity Measurement

Low humidity weakens the immune system, dries out the mucous membranes, and leads to skin irritation, burning eyes, and reduced respiratory performance. This weakens the body and also promotes viruses and bacteria staying airborne longer – the risk of infection increases. When the air is more humid, however, pathogens become enveloped in a film of water. Their mass then increases, along with their settling speed. They essentially end up on the ground. Another problem with humidity that's too low: dust is stirred up more easily. This is especially hard on allergy sufferers. And: when the air is very dry, static electricity builds up more often, discharging when we walk across a carpet or touch metallic materials.

Excessive humidity promotes discomfort and circulatory problems, impairs productivity, and encourages mold. High temperatures combined with high humidity become unpleasant, since the body can't cool itself through sweating. That's because evaporation is limited, as the surrounding air can barely absorb any more water. A film of sweat remains on the body.

When mold spores enter the body, conjunctivitis, gastrointestinal issues, joint pain, asthma, or migraines occur more frequently. Above a relative humidity of 60%, dust mites also multiply, releasing more allergens and burdening allergy sufferers.

However, humidity is perceived differently by different people. These impressions are subjective and can easily be wrong. It's therefore advisable to check absolute humidity objectively. An air quality monitor like the air-q helps here, continuously measuring humidity and issuing warnings if threshold values are exceeded.

What helps against excessive humidity?

1. Place a bowl of salt in the room. The crystals bind moisture.
2. Keep showers as short as possible & avoid water vapor when cooking, e.g. (turn on the extractor hood).
3. Maintain the recommended room temperature.
4. Measure absolute humidity with an air quality monitor like the air-Q and burst-ventilate regularly.

What helps against humidity that's too low?

1. Use a humidifier: either a dedicated device or natural humidifiers such as plants that need a lot of water, are watered accordingly, and release moisture back through the soil and their leaves.
2. After showering or cooking, distribute the resulting moisture into other rooms through open doors.
3. Avoid an unnecessarily high air exchange rate, for example from permanently tilted windows, leaky doors, windows, or chimneys.
4. Measure absolute humidity with an air quality monitor like the air-Q and burst-ventilate on an as-needed basis.