Exhaust fans

Exhaust fans are electrically powered devices that support the operation of gravitational ventilation (i.e. one that works thanks to convection, i.e. air movement caused by ró the difference in its density and pressure - air with a higher temperature has a lower density than cooler air, which is why it rises, so warmer air from the building gets outside, e.g. through windows, openings and cracks). As the name suggests, this type of fans is used to exhaust used air outside the building. Therefore, it is not responsible for the supply of fresh air, for which the supply fans are responsible.

If a gravity system is no longer efficient, consider mechanical support. Room ventilation is considered ineffective if the requirements of the Polish Standard PN-83/B-03430/Az3 are not met. This provision mentions the requirements for the amount of air needed to ventilate individual rooms in residential buildings (both single-family houses and blocks of flats) and public utility buildings.

How can you tell if the ventilation is not efficient enough? The following symptoms of lack of fresh air may appear in rooms, such as:

• mold and fungus (e.g. on walls),
• condensed water vapor (e.g. on windows or tiles)
• increased levels of air humidity,
• backdraft of air in ventilation grilles (inflow of stale air, dust, odors from the outside, exhaust fumes, cigarette smoke, etc.).

An important signal that may indicate defective ventilation may also be the deformation of elements made of moisture-absorbing materials (e.g. wood, wood-based materials, gypsum).  

Residents who spend a long time in rooms with poor ventilation may experience:

• head aches,
• excessive fatigue,
• irritation of mucous membranes,

Over time, this condition can even lead to respiratory diseases and allergies.

How to install exhaust fans

To support gravity ventilation, the fans are mounted in the inlet of the ventilation duct instead of standard grilles. There are also duct models that are mounted in the duct itself, which, however, in some situations may hinder or completely prevent the gravitational air flow (when the fan is turned off).

The fan is therefore the end of the duct and is usually the visible part of the ventilation. Therefore, for aesthetic reasons, these devices are available in various colors and finishes, e.g. made of plastic or stainless steel. The fan does not have to be white, it can be color matched to the color of the walls, tiles or fittings.

When choosing a specific model, the diameter of the connection element should be additionally taken into account so that it is appropriately matched to the dimensions of the channel.

Types of exhaust fans

There are two types of this type of equipment:

• axial fans - air movement takes place along the axis on which the impeller is mounted.
• central fans - air flows perpendicular to the axis.

In addition to universal models, there are also specialized solutions, such as:

• bathroom fans - designed for rooms with high humidity (should be splash-proof). Models installed in shower cabins are characterized by a low voltage power supply.
• central fans for kitchen hoods - designed to remove vapors generated during cooking. They can be additionally equipped with a protective mesh against grease.

The el12.pl assortment includes devices from various manufacturers. We offer exhaust fans with a power of 0.96 to 24W, rotational speed in the range of 1500-3600 RPM and air flow in the range of 95-2500 m2h.

How to choose the right exhaust fan?

When choosing a fan, keep in mind, among others: about:

• minimum ventilation requirements for given rooms,
• mounting location (wall or ceiling). This is important because not all fans are suitable for ceiling mounting. Duct or flow fans can be mounted above the suspended ceiling or in the wall and other invisible places,
• diameter of the vent (standard sizes are 100, 120 or 150 millimeters),
• power supplied to the vent (220V or 12V),
• required cable for connection (e.g. fans with additional timer function may require connection to a three-wire cable).

Additional functions of exhaust fans

When choosing a model, it is also worth considering what additional amenities it will have (which of course will also translate into the price). Depending on the model, exhaust fans can be equipped with the following functions:

• return flap - is designed to prevent the backflow of air, i.e. the inflow of air (and thus - impurities) from the ventilation duct into the room. This function is particularly important when the ventilation stack is used by several users and e.g. cigarette smoke, the smell of food, and even sound from other apartments may be transferred. The operation of the damper is based on the fact that it is always closed when the fan is not operating. When the device is turned on, the flap opens automatically by the force of the airflow to smoothly drain gases and impurities from the room.
• timer switch - it works in such a way that the fan starts working e.g. at the same time as turning on the light in the toilet and continues to work for some time after turning off the light. Depending on the model settings, it can be from about a few to more than 20 minutes, after which the device turns itself off. This function allows you to ventilate the room every time someone uses it.
• control - most often these devices are controlled with a switch (manually), although more advanced models allow, for example, to program cyclical operation.

Additional sensors in exhaust fans

More advanced models of fans can also be equipped with a number of sensors, among which the most common are:

• light sensor - often used in restaurants, shops and public buildings. The fan is permanently connected to the power supply and does not require a separate switch, because it starts working when the light in the room is turned on. The device will automatically pause when the light turns off.
• humidity sensor – it works in such a way that the device starts working after exceeding the set humidity (e.g. about 70%) and stops when the value drops below 70% and when the time indicated in the settings has elapsed. This solution will be especially useful in a bathroom with a shower.
• motion sensor – the fan activates the motion detection and the device will run e.g. for a programmed time after the motion stops. When deciding on such a solution, however, it should be remembered that the motion sensor cannot be covered, it should cover the entire room, and all elements that may unnecessarily activate the fan must be eliminated.
• temperature sensor – it is used in duct fans installed in the spaces between ceilings or in the vicinity of the fireplace. The thermostat switches the fan on and off automatically when the programmed temperature limits are exceeded.

When considering the model, it is also worth paying attention to what filter the fan is equipped with (this helps prevent insects from entering the room).