Filter stages are indispensable in ventilation equipment. They protect the equipment from external agents that may affect it or are used to prevent contaminants from entering through the ventilation ducts in places that must be sterile (operating theatres, clean rooms, etc.). Let's take a look at the types, the rules that govern them and their usual application.

As they are components that are in contact with contamination and dirt, it is very important that these filters are properly maintained. Thereby, it's ensured their optimal functioning and, above all, that they are replaced at the times specified by the manufacturer or the device alarm.

But what is a filter? A filter is a component designed to reduce the concentration of solid particles in the air. There are different filter stages, which are generally: metal mesh, filter bags, filter media, plant or activated carbon filters, HEPA filter and HEPA or ULPA terminal filter (depending on the application). Air filters must take two factors into account to be effective:

• The size of the particles in suspension.
• The degree of concentration of the particles: dust, smoke, pollen, odours, moisture, ...

Filtration capacity

Pre-filters: they are those stages that are included in the suction phase of the device and prevent the entry of larger objects such as leaves, insects, small rodents, or other large contaminants into the system.

At Airtècnics we have the Metallic Z-Line filter. It is a metallic filtering stage made of galvanized sheet metal with zig-zag synthetic fibre media. According to EN 779 standard it is classified as G4 and the ASHRAE efficiency is 95%. And it can be included in most ventilation and air purification equipment such as any model of K7, Cyclohnic, Kleenbox or Dif-Pur.

This category includes Diedrik and Multibag filters from Airtècnics catalogue.

• Multibag: filter bags thermowelded to a polyurethane frame. As they do not contain PVC or alogens, they are environmentally friendly. This filter does not provide any nutrients to encourage the growth of micro-organisms.
• Diedrik: fibreglass filter with a rigid polystyrene frame.
• Carbo-pack filter: made of activated carbon for the elimination of gases and bad smells. It is available in two models, depending on the composition: granulated or with fibres and microfibres. They should be combined with a high-efficiency filter to optimise their efficiency and durability.

At Airtècnics we also have the absolute filters:

• Lamiflow, filtration stages H14 maximum filtration and absolute efficiency (efficiency up to U17, under request). The filter has a metallic protection grid on both sides to avoid damages. Available in two models depending on the gasket, which can be polyurethane or liquid gel-silicone. Also available in different dimensions depending on the air flow requirements of the installation. Compatible with Dif-Vent and Dif-Pur filtration units, for spaces where air quality cannot be compromised.
• Absor / Poli-absor filter: high efficiency HEPA absolute filter, capable of retaining MPP10 particles, such as tobacco smoke, bacteria, viruses and other air pollutants of organic origin, as well as those of chemical origin. It is the ideal complement to Dif-vent and Dif-box air diffusers.