The term air humidity is used to indicate the amount of moisture in the air. Outside, the air humidity can change with the weather, while indoors or in the office the air humidity can also change daily because of the weather, but also because of ventilation.

The relative air humidity is given as a percentage. The percentage of vapour measured with respect to the maximum volume of vapour in the air. In the Netherlands the average outdoor air humidity lies between 60% and 80%. However, this can also vary to between 5% and 100%. With a relative humidity of 100%, the maximum volume of moisture in the air is reached and that is more than likely rain.

The relative humidity in a house or office is often held at around 40% to 60%. This is the general level for a healthy atmosphere and is good for the proper functioning of your airways.

Formula for low air humidity*

You probably think that the lowest air humidity occurs on a hot summer’s day, but this couldn’t be further from the truth. Warm air can actually absorb a lot of moisture. The lowest relative air humidity can occur on a cold winter’s day when the sky is clear and blue. Whenever the wind comes out of the north-east and the temperature rises rapidly during the day and falls equally rapidly at night, this can lead to a relative air humidity of around 20 per cent. The Royal Netherlands Meteorological Institute at the Deelen airbase measured a relative air humidity level of just 18 per cent on 23 March 2013!

Consequences for sealing and bonding

Low relative air humidity levels have consequences when using a number of Bison products. There are adhesives and sealants that require the ambient humidity to cure completely. Silicone Sealants and Poly Max®, for example. But there are also adhesives such as Super Glues that use moisture to harden. Therefore, watch out when the relative humidity is low as these adhesives and sealants will take much longer to cure. Light moisturising using a plant spray, for example, will help to speed up the curing process.

Consequences for the operation of Moisture Absorber

Bison Moisture Absorber Original is unable to operate normally with low relative air humidity levels. There is simply not enough moisture to remove from the air. This can occur even when you see moisture on window panes. The windows act as so-called thermal bridges, where any moisture still present will end up on the glass first. This is because it is cold outside and warm inside. The moisture condenses on the glass window panes. Bison Moisture Absorber Original starts absorbing moisture as soon as the level of relative humidity rises again.