The ventilation box within mechanical ventilation systems

The double-flow mechanical ventilation is, without a doubt, the best forced ventilation system as it ensures that the indoor air of our spaces is free of contaminating particles and therefore healthy. Within this controlled ventilation system —the extraction and supply volume, and the hygrometric characteristics of the air can be regulated, regardless of the humidity content in the outside air— the ventilation box plays a fundamental role.

Regulatory requirements for the ventilation box

According to the current regulations on indoor air quality in premises (CTE DB HS 3), the ventilation box of the system must meet the following three requirements:

• It must be located in such a way that it is easily accessible to facilitate maintenance and cleaning.
• It must have a system that prevents the inversion of air flows at all points.
• It must be sized according to the supply flow and for a pressure capable of neutralizing the pressure losses of the system.

Recommendations

It is advisable to avoid the formation of whirlwinds in the incoming air flow to the extractor. These vortices can occur due to poor design or the presence of numerous elbows in the duct layout. If it is impossible to avoid the presence of elbows near the ventilation box, the implementation of guide fins (or air flow rectifiers) is recommended to minimize this effect.

We must ensure that our equipment provides high-quality supply air and extracts the stale air that accumulates internally as a result of the regular use of the premises. To do this, the ventilation box must incorporate an efficient extractor that guarantees a high flow rate and maximum system performance, regardless of its operating conditions. This box, in order to ensure the acoustic comfort of the occupants, must be perfectly insulated and soundproofed, using sound-absorbing materials for this purpose.

Other elements of the ventilation system: filters

Regarding the filters of the system, which are essential for filtering the supply air, we must ensure that they are G4 or F7:

• G4 (for supply and extraction). They are capable of capturing pollen, spores, molds, and fine particles.
• F7 (for supply). Capable of filtering pollen, spores, molds, and fine particles, as well as bacteria and viruses contained in the air.

Remember that a series of maintenance and cleaning actions of the filters must be carried out. They should be cleaned once every six months and replaced once a year. Clean and well-maintained filters will reduce energy consumption (as they will not force the system) and ensure maximum comfort (as noise will be reduced, and better indoor air quality will be guaranteed).