FM Articles

Facts vs. Fiction: Your Air Cleaner

Air Cleaner

People, including businesses, spend tens of millions of dollars worldwide, every year on air cleaning solutions, but many of them don’t know what they are actually buying and how effective their air filtration is for their specific needs.

Below, you’ll find information comparing the advantages and disadvantages to different types of air filtration techniques, in helping you discover the most beneficial air filtration system for yourself and your specific, indoor environment. We’re also including tips to spot “questionable claims” from manufacturers.

The Placebo Effect
With regards to this topic, “assumption is the mother of all failures”. Just because we think our air is being sufficiently cleaned, doesn’t mean it actually is.

Unfortunately, there are popular “air purifier” brands making claims that are only true under certain circumstances or for a limited time, but the power of suggestion is a strong marketing ploy. One of the most popular ones is, “Takes away smells/odors”. Other claims are, “Takes away 100% of smoke” or “100% of all airborne particles”. Let’s look at these claims a bit closer and single out what are important facts about air cleaners.

So, you have a great air cleaner. Is it in the most beneficial place to clean the air?

Placement is equally important when choosing and using an air filtration system. Unlike a home entertainment system’s subwoofer, placement is everything!

Businesses especially need to be aware of this more than consumers, because of the size of facilities as well as the amount of traffic, gases and air particles that go through and accumulate at businesses. People, products, byproducts, and outside influences make business environments more susceptible to poor air quality.

Filters and Capturing Technology
Common causes of air contamination deriving from the indoor are: People, pets, candles, VOCs, aerosols from cleaning products, dust mites in carpets and curtains, smoke, gas from stoves, building materials, radon, gases emitted from certain types of upholstery and furniture, indoor plants releasing pollen, plus many more!

Filtration technology and filter type are important when choosing an air purifier and depend on what you want to capture, as well as, for what purpose you are using it for. Find out what kind of filter and filtration system your air cleaner has, or if you’re looking for advice on what kind to get, here are a few tips.

Particle Filtration

  • Mechanical filters are a common way of filtering particles and use a fine fiber weave. They come in many different types for different purposes and classified according to different standards. When using mechanical filters, you usually use at least 2 filter layers for safety reasons, and to increase the capacity of the system. First, a coarser filter is applied that captures big particles like pollen, household dust etc. In a second step, a fine filter is applied that captures the fine particles form e.g. combustion. Typically, fine filters are of classification EPA or HEPA according to standard EN1822 and with a high guaranteed filtering efficiency that lasts over time. The HEPA filters are each individually tested to guarantee performance, also over time.
  • Electrostatic filtration is another common technology for filtering particles. It is based on the electromechanical principle that positively charged items are attracted to negatively charged ones. Particles in the incoming air are charged when traveling through a corona field and are then attracted to and stick on negatively charged plates in the air cleaner. This solution is energy efficient as there is no big resistance in the air flow from a filter like in the mechanical filter solution. You do not have to change filters either, you simply wash the plates. The downside with this solution is that the efficiency at which the solution captures particles is diminished as the plates start filling up. The more particles captured the less space for new ones and the more likely they will travel straight through the air cleaner. So, if you do not wash the plates frequently, you will easily end up with an air cleaner that acts like a fan rather than as an air cleaner. Additionally, there is no classification for electrostatic filters.
  • In some air cleaners, you also find electrostatically charged mechanical filters. You may say this is something in between the two systems mentioned above. These filters are basically a mechanical filter of lower grade that has been electrostatically charged in production in order to have the capturing efficiency of a higher graded filter. This has the advantage that the resistance in the filter is lower and a smaller fan can be used to achieve the same airflow. The downside to this is, as the filters fill with particles the charged surface diminishes, along with its capturing efficiency; just like an electrostatic filter.

The difference is that capturing efficiency will always remain at the mechanical filter grade it has been built upon before charging it. A warning is that some gases flowing through a charged filter will actually discharge it very quickly; an example of one such gas is isopropanol. Filters called “HEPA” + an additional name are often of this category e.g. “HEPA Max” or “Quality HEPA” and cannot be called HEPA because they cannot live up to the quality standard but like to ride on the name of HEPA for marketing purposes. Only HEPA filters that fulfill the EN1822 standard can be named “HEPA”.

Gas Filtration

  • Carbon filters are a common type of filter to capture a broad spectrum of gases. Gases are adsorbed in the fine captivities of the activated carbon. The guiding principle is: the more carbon and the thicker the bed of carbon is, the more capacity the filter has to capture gases, and the more secure you can be that actually works. You cannot see on a carbon filter when it is full. You either have to measure how much is released at the outlet compared to the concentration on the inlet, or you need to have control of how much gas you have added to the filter. When the carbon filter is full it needs to be replaced and taken care of according to local environmental regulations depending on what it might have captured.
  • UV and photocatalytic filters aim at breaking down the gas molecules into harmless substances like water and carbon dioxide rather than capturing them. When designed right, this is a good solution but there is always a risk that this process is not completed due to factors like gas concentration or humidity which goes outside the boundaries of the system’s design. You will then have rest products from the process added to the air from the outlet of the air cleaner. This means, instead of cleaning your air, the air cleaner adds new harmful substances to your air, typically such substances are formaldehyde and ozone. Why is this important? Ground-level ozone is an air pollutant that is harmful to breathe, and it damages crops, trees, and other vegetation. … The stratosphere or “good” ozone layer extends upward from about 6 to 30 miles and protects life on Earth from the sun’s harmful ultraviolet (UV) rays. (Source)

The efficiency of an air cleaner is a function of the product based on airflow and filtration efficiency. Without a good air flow, it does not matter how efficient the air cleaner captures gases or particles. Many filtering technologies restrain the air flow over time as resistance is built up in the filters when they get “fuller” with particles.

Some advanced air cleaners have their fan compensate for this increased resistance over time and the fan revs up to make sure it always delivers the same volume of air.

No matter if the air cleaner has this functionality or not, it is important that it signals when the air flow gets too low and it is time to change filters.

Filter Maintenance
No matter which filter technology you chose, all air filtration technologies require maintenance. Either filters are simply replaced or need to be cleaned before being reused.

However, it is of utmost importance that this is done when needed; otherwise, you have an air cleaner that does not work. Either all contaminants go straight through the air cleaner or the air cannot get through the unit as the filters are blocked.