The ceiling extractor. Characteristics of localized ventilation

General characteristics of ventilation

Ventilation can be defined as the technique that allows the replacement of air in the interior of a space that is considered inadequate due to its degree of contamination, an inappropriate temperature, or excess humidity, with external air that has better characteristics. In the case of people, ventilation is used to fulfill vital functions such as providing oxygen for respiration and controlling the heat produced by the human body. In the case of machines and industrial processes, ventilation allows controlling heat, toxicity, or the potential explosiveness of the environment.

Localized ventilation

In this type of ventilation, contaminated air is captured in the same place where it is produced, preventing its diffusion throughout the space. Localized ventilation is achieved through a hood that surrounds the source of polluted air and directs it straight to the outside. Therefore, the process to follow is: first, identify the points of contaminant production, then encase it under an extraction hood, and subsequently establish a suction capable of capturing, dragging, and transporting the air loaded with particles.

The basic elements of this installation are:

1. The capture
2. The duct or channel
3. The separator or filter
4. The extractor fan

Regarding capture, its mission is to attract contaminated air to transport it to the discharge point. In its design, the following aspects must be considered:

• The capture flow varies approximately with the square of the distance, meaning that if the hood is at a distance L from the source and needs a flow Q to capture it, if it moves to a distance of 2L, the required flow to capture the same volume of air will be 4Q.

• When dealing with harmful gases, the hood must be placed so that the contaminated air can be evacuated outside the breathing space of the workers.

• Whenever possible, the extraction nozzles should have a flange, which allows reducing the flow by 25%.

The ceiling extractor

In conventional extraction systems, air is expelled through ducts and the environment is renewed with clean air from outside the premises. The ceiling extractors currently used have a recirculation system that allows renewing the air within the premises itself, thus achieving considerable energy savings. The ceiling extractors can be:

Atmospheric extractors: these are extractors for the roofs of warehouses or industrial buildings. Made of aluminum, they are activated with a temperature difference of 3°C between the inside and outside of the building, circulating air at 8 km/h. This way, the generated noise is minimal.

Extractors for kitchen hoods: These are made of aluminum and are weather-resistant. They can withstand the introduction of contaminated air with grease.

Direct ceiling extractors: These are designed for use in the ceilings of offices, meeting rooms, schools, and other public spaces where it is necessary to minimize acoustic contamination and energy consumption. To achieve this, they use a balanced aluminum fan with three blades.