The intumescent grill in ventilation systems

The air diffusion inside a room is a very important part of the ventilation process. It consists of distributing an air flow in a uniform manner and at a speed that is not bothersome to the occupants. Through the impulse, the air from the environment must be drawn in and mixed with it outside the occupied areas, ultimately reaching a very low terminal speed that does not disturb the building's users. When predicting air displacement, a series of parameters must be considered, such as those outlined below:

• Efficiency: it is the ratio between the concentration of a contaminant at the extraction point and the concentration that is contained on average in the occupied area. Its value is usually less than one.
• Reach: It is the distance that the air flow reaches before its speed decreases to the terminal, which is generally 0.25 m/s.
• diffuser: air outlet supplying in various directions and planes.
• Effective area: it is the net space of an air intake or extraction mouth.
• Drag coefficient: the ratio between the air moved in a room and the air propelled by an impulse mouth.

The relative position of the grills and diffusers at the intake and extraction mouths is also very important in obtaining a correct air diffusion. When it comes to rooms with a regular shape and not too large, some of the following distributions are usually used:

• Two mouths with wall-mounted impulse and extraction grills, placed on the same partition or enclosing wall.
• One diffuser placed in the central area of the ceiling and a extraction mouth in the lower part of one of the partitions that delimit the room. When the room is rectangular, this last one must be located on one of the shorter sides of the room.
• Two floor diffusers located at two opposite ends of the room. They should be placed in areas where no occupants or any type of furniture that may hinder the ventilation process is present.
• When the space to be covered is very large or has an irregular perimeter, the air diffusion must be zoned, orienting the diffusers so that their discharges cover the entire room without overlapping.

The intumescent grill: general characteristics

The intumescent grill is usually designed to be installed in partitions or doors to facilitate the circulation of air between two rooms. At the same time, it must prevent the spread of fire in case of a fire. If it occurs, the slats that form the grill expand covering their openings and forming a barrier against flames and gases. The frames or perimeter profiles are made of thermoplastic materials with intumescent properties that begin to expand when they reach 100°C. These grills are especially suitable for installation in fire-resistant doors, whether metallic or wooden.