How does a dehumidifier work?

Dehumidifiers are not as well known, popular or common as humidifiers, but they can have a huge impact on the air quality and environmental conditions in a building. Even if you know they exist, you’ve probably never thought about how they actually work – especially on an industrial scale. We at Best of Machinery have put together this brief explanation of what they do, how they work and why they are so important.

The basics

Humidifiers add moisture to the air, and dehumidifiers are supposed to do the opposite: they extract moisture from the air and dispose of it at another location, resulting in a net loss of moisture, which affects the feeling of space and the atmosphere. This can help protect furniture from moisture damage, remove mold and prevent skin damage from excessive moisture exposure. It can also affect the average temperature of the room or building. Keeping an area dry can be even more beneficial in industrial environments, but we’ll cover that later.

Commercial dehumidifiers come in several variations, but all serve the same purpose. Below are some of the most popular types. However, keep in mind that these are not all, especially not when counting DIY designs.

Refrigerant dehumidifiers

These work through condensation and are some of the most common as they are often built to work automatically without the need for manual verification or input. Most designs use a cold evaporator coil to cool the air that enters them and condense the water vapor into droplets without also freezing the air. This literally completely removes the water from the air, dries it up and sends it back into the room.

The drops of water are then collected in a pan, hose, or other disposal method and removed from the room. Because they are often completely clean, certain systems return this water to a reserve tank for later use, but others simply dispose of it entirely through a drain or pipe instead. Because they are based on cooling the water, they can fight in colder conditions.

Desiccant dehumidifier

These types use a moisture absorbing material to collect water from the air flowing through it, which is then heated in a separate section to evaporate the water back into moisture that is conducted out of the building. Technically, this can work both as a dehumidifier and as a normal humidifier, since the water vapor is simply transferred from one room to another, but is often used instead as a one-way system.

Desiccant dehumidifiers can operate at very low temperatures, but must be constantly powered and will normally only work when powered. They are the most common type in industrial buildings because the power requirement is less problematic when the building is already filled with machines.

Dehumidifiers for the whole house

Whole house structures are the exact opposite of building-wide humidification systems in which fresh air is forced into the building to expel the air filled with moisture. These are often mounted on attics, ceilings and other high areas so they can work down. This means that they first freshen the air in the highest rooms.

You will usually see them in office buildings and other tall buildings because they work best when they collect air from above.

Ion membrane dehumidifier

As one of the most complex types, ion membrane dehumidifiers use an electrolyte membrane to remove water molecules through electrolysis. This does not consume much electricity, but it also cannot remove much moisture at once, making it resemble a much smaller scale desiccant dehumidifier. However, they do not require a lot of maintenance, so they can generally be set up and left in a room without having to be repaired or replaced.

Industrial models

Industrial dehumidifiers are often used to remove moisture that could damage important equipment or render the material unusable. They are generally only larger versions of standard, longer-range dehumidifiers. They are sometimes used together with humidifiers to ensure a constant supply of “fresh” moist water or to keep the humidity at a certain level without completely removing it.

Sometimes they also appear during construction work, especially in open areas that offer no protection against bad weather or mold. These are sometimes temporary ones that are set up during the construction process and removed after the building is completed.


Once water drops and / or moisture are collected, there are several ways that they can be disposed of. Many portable dehumidifiers contain sensors that automatically turn them off when they’re almost full. This signals to the owner that the water has to be drained off somewhere before it can continue to be used. However, some can be connected to pipes so that they can be connected, pumping the water away from the building continuously instead of slowly filling up.

Dehumidifiers that are mounted on a building are either self-contained or connected to the building’s water system, depending on whether it is clean enough to be reused. If it is too dirty, it is usually only routed to a drain or sewer pipe and very rarely stored for further use.

Dehumidifier systems for the whole house usually work in a similar way, taking water from each room and disposing of it through a pipe system. Since it is a larger volume of water, these pipes can be connected to other sewage pipes, such as those used in bathrooms.

Leave a Reply

Your email address will not be published. Required fields are marked *