The closed environments they tend to accumulate dust, pollen, light chemicals, microorganisms and odors more than outdoors, because our own daily activity introduces and traps these contaminants. Those who suffer from allergies, asthma or have particular respiratory sensitivity may be more affected by unhealthy environments, and in these cases the reduction of particles through the use of air purifiers it often translates into a concrete benefit, already tangible in the short term. But how these devices work? It depends on the type of purifier, given that not all purification systems are the same: some use mechanical filters, others still use ionizers and ozone generators, still other systems exploit germicidal UV light or the use of adsorbent materials. Let’s see in more detail how all these systems work and try to understand when purifiers should be used in domestic or office environments.
What is an air purifier and how does it work
If we look closely at what happens between the walls of the home, we discover that indoor air tends to accumulate contaminants: we export dust and pollen from outside, we continuously generate skin and hair residues, we cook, we use chemical products and we operate heating and cooling systems that recirculate everything that settles in the ducts. In the presence of humidity furthermore, molds and spores find an ideal environment to proliferate. Without falling into dangerous alarmism and various paranoia, this does not mean that our homes are in themselves dangerous spaces, but this reflection reminds us that, especially for some more fragile categories, even small variations in air quality can improve the quality of life, or worsen it. This is where the logic of using a purifier arises at times or places where the concentration of allergens and particulates increases. To understand how air purifiers workwe list the 5 main technologies with which these devices work.
- Mechanical filters: they force air to pass through porous materials (such as foam, synthetic fibers, cotton, or fiberglass) that trap particles. When the material is very dense and the surface area is large, as happens in pleated filters, the capacity to retain small particles increases. THE HEPA filters (High Efficiency Particulate Air), which respect the penetration threshold lower than 0.03% for particles of 0.3 micrometersare a widespread standard because they guarantee measurable performance. Those ULPA (Ultra-Low Penetration Air) are even more selective, but are mainly used in industrial contexts. However, these filters need to be replaced regularly and reduce airflow slightly, so cost and maintenance needs to be considered.
- Ionizing purifiers: they exploit the so-called corona discharge, a phenomenon in which the electric current passes from a conductor with high electrical potential towards the neutral fluid that surrounds it and which occurs when an intense electric field is able to modify the charge of the particles in the air. An ionized particle tends to stick to a plate of opposite sign or aggregate with other particles, becoming heavier and depositing. It must be said that various independent tests have shown that the actual reduction in suspended particles is often minimal. And, although these systems generate small amounts of ozone as a byproduct, the real critical issue lies in the devices designed to produce ozone.
- Ozone generators: these modify oxygen molecules through electrical discharges or UV radiation, transforming them into ozone, an unstable molecule that easily reacts with other substances present in the indoor air, generating secondary compounds. Manufacturers often claim that this helps to neutralize odors or microorganisms, but studies also conducted at the request of theEPA (United States Environmental Protection Agency) indicate that ozone does not clean indoor air effectively and that, at relatively low concentrations, it can irritate the respiratory tract. The EPA, after testing on various models, found ozone levels higher than recommended limits even following manufacturers’ instructions, as well as the formation of unwanted by-products resulting from chemical reactions with compounds present in the environments. For this reason, the US Environmental Protection Agency calls for preference for already consolidated methods and does not include ozone generators among the recommended solutions.
- Adsorbent Purifiers: purifiers based on this technology use materials, such as activated carbon, that retain odorous molecules or volatile compounds on their porous surface. Adsorption (not to be confused with absorption) is the process of trapping one substance on the surface of another substance. In this process, microscopic pores of activated carbon (or other suitable materials) are exploited which trap passing molecules, making this method particularly useful for neutralizing odors and fumes (less useful for capturing dust and pollen).
- UV lamps: the devices that integrate them are able to inactivate viruses and bacteria exposed to radiation.
When and why to use an air purifier
Now we come to the question of questions. When is it advisable to use an air purifier? Certainly in all those cases where there is someone in the home or office who suffers from allergies, asthma or other breathing difficulties. Jill Heinssenior director ofAmerican Lung Associationin fact it says that in reality, in the presence of an air quality index of 150 or higher «everyone should consider using an air purifier».
