Air filters come in various types. There are air filters that contain chemicals that enhance their functions and there are simple air filter that use only a fibrous material to filter air. Some air filters are used specifically for pulling allergens out of the air—HEPA—and some are designed to be far less selective, lowering the levels of dust taken into an engine, for instance.
While filters are simple looking devices, their workings are complex in some regards. The various materials used to make them and treatments given them mean that there are many different types available on the market, as well. It’s important to understand their differences and their history.
Over time, the filters available to everyday consumers have become more and more sophisticated. They have also become more affordable, making it possible for homeowners to vastly increase the quality of their indoor air. At the same time, advances have made it possible for people to enjoy much healthier work environments due to improvements in air filtration. Dust levels can be greatly reduced in factories and warehouses. For workers who labor in mines, personal filtration systems are advanced enough to ensure that they can work safely in very dangerous circumstances.
Some filters are sold as parts of kits. While the filtration materials in the filters may be rather sophisticated, in some cases, installing and operating these filters is usually very simple, as it has been since they were introduced. The filter need only be placed so that it provides a barrier between air that needs to be cleaned and air that has already been cleaned. This makes it possible to change entire filter systems very easily by simply swapping out a frame, a filter and the other hardware involved in installing the systems.
What are air filters?
Air filters are devices that remove contaminants from the air. They do this by forcing air to pass through a material that only allows particles of a certain size to pass through them. They may use sophisticated methods to channel the air, such as fans and other mechanical devices. They also use simple human respiration to do the job. Gas masks are good examples of this. The force of the person inhaling moves air through the filters on the mask and, combined with a seal that prevents air from entering the airways otherwise, this allows all the air that the person inhales to be filtered before it reaches their lungs.
Air filters can be made out of any number of different materials. They can be made from paper, fiberglass or far more advance materials. Most air filters are pleated. This allows more surface area to be dedicated to filtering the air, which helps to clean out particulates more efficiently. Filters may also have multiple layers or another engineering features that makes it possible for them to pull more contaminants out of the air.
Air filters are different from air purifiers. Those latter devices usually have electronic or other components that clean the air to a greater degree of purity. They are oftentimes combined with a filter. The filter removes its share of contaminants and the purifier augments this function by removing contaminants that the filter may not be able to catch.
An air filter will be rated by what percentage of particles over a certain size it will allow to pass through. HEPA standards, for instance, dictate that the filter should only allow particles smaller than .3 micrometers to pass through and, even then, only .03 percent of the particles of that size that contact the filter’s surface should make it through. This is, obviously, a very high standard, but that is what makes these types of filters so popular. They can remove everything from pollen to certain types of radioactive dust from the air, so they have myriad different applications and have become the standard for most air filtration systems.
What are air filters used for?
The main purpose of an air filter is to reduce or outright eliminate particulate contaminants from the air. Sometimes, they are provided with treatments, such as charcoal, that chemically react with substances in the air and change them so that they are safer to breathe. Charcoal filters, for instance, have been used to neutralize even chemical warfare contaminants in the past.
More sophisticated air filters can be used for more demanding purposes. HEPA filters, for instance, can be used in areas where radioactive particles may be a hazard. Other types of air filters may be used under equally specific circumstances. Most often, higher-technology air filters can perform better for general purposes than older designs, which has made it very common to see HEPA filters on objects such as vacuum cleaners, smoke eaters and so forth.
The differences in air filters and how they dictate their uses can easily be seen on the consumer market. Homeowners who are doing some minor repairs may get a dust mask, which is a primitive air filter that uses a fibrous material to remove dust from the air the wearer is breathing, but they may get far more advance filters for installing installation or other jobs.
Some of the uses of air filters include:
- HVAC systems
- Clean rooms
- Hospital hygiene
- Filtration for electronics systems
- Firefighter gear
- Vacuum cleaners
- Engine air filtration
It’s imperative that the right filter is used for the job at hand. Using filters that do not specifically remove certain types of contaminants could cause trouble for people exposed to a dangerous interior environment. For people with allergies, using a filter that doesn’t meet the definition of a HEPA filter could mean that they are still exposed to far more allergens than they should be, causing myriad problems for them as they react to the materials in the atmosphere.
History of air filters
The first patent ever issued for an air filter was issued in 1849. Lewis Haslett may have been the first person to patent an “Inhaler or Lung Protector”, as he called it, but there was a previous design that dated from 1820. That design was intended for use by firefighters.
The history of air filters is very much tied to finding ways to deal with the most hazardous situations, though air filters today are oftentimes used for much more mundane purposes, such as lowering the levels of dust that a vacuum cleaner kicks out.
Miners, firefighters and other workers face hazards that are directly related to particulate and chemical pollution of the air. When firefighters finally got a personal respirator that they could carry with them on their backs—in the 1870s—the technology that would eventually be used in one of the deadliest wars ever fought was already developed. That technology would be gas mask technology.
Gas masks use a chemical to filter a certain substance out of the air or to neutralize it. The development of this technology accelerated considerably during World War 1, in which chemical weapons were widely used. These advances played into the way that modern air filters came to function.
One example of this is called adsorbency. This describes a process where a material is actually added to the air. Activated charcoal, for instance, will trap impurities on its surface, allowing them to be removed from the air. Other materials may be used in the same role.
As science advanced, radiation hazards became very real threats. To filter out radioactive materials from the air, a superior air filter to other designs was required. This need led to the development of the HEPA filter, which makes spring and summer more tolerable to allergy sufferers around the world. These filters are incredibly precise and are able to filter very small particulates out of the air. They may be inexpensive today, but they were the pinnacle of air filtration technology in the early nuclear age.
New air filters use even more advanced technology. Common particulate air filters, which drag air through a filter and expel it after it has been scrubbed by the filter, are still very popular and effective. Many of the designs intended for the consumer market come with electric air filters on them now. These purify the air by removing some types of contaminants that filters may be unable to, such as spores and viruses.
There are some very significant differences in industrial and consumer air filters, even though they may use much of the same technology. Industrial air filters are generally much more durable and the systems to which they are attached are much more powerful. Nonetheless, the effect of the systems failing is the same. Whether a filter isn’t replaced on schedule in a homeowner’s furnace or on a very large piece of industrial equipment, the clogged filter impedes airflow. This affects the performance of the system to which it is attached. At the same time, the filter being completely full of contaminants means that it can no longer remove contaminants from the atmosphere and that the air quality may rapidly decline. In vehicles, dirty air filters cause compromised performance and gas mileage.
What are Air Filter Clips?
Air filter clips are used to hold a filter in place. In order for a filter to work properly, the air flow around the filter has to be controlled so that minimal particles are allowed to pass. The filters, when put in place, are subject to forces exerted by moving air, which can displace them in their mountings. The clips provide security. They are inexpensive and are clipped at the edges of the filter, if the filter is straight, and at the perimeter, if the filter is round.
What are Air Filter Frames?
Air filter frames provide a way to mount air filters in the ventilation in which they are installed. They usually have an outer frame to which clips can be added and an open area where the filter sits. They typically have a grate that protects the filter from larger particles damaging it and that give it support.
Air filter frames come in many different sizes. Some equipment may have the frame built into the system, such as a furnace that merely requires the user to slide filters in our out without actually opening up the entire frame.
What are Fan Filters?
Fan filters combine the fan with the air filter itself. This is very useful in situations where compactness is an issue, such as in computer cases, where these devices are sometimes employed to cut down on the levels of dust that build up in the case with use.
Fan filters are also convenient when a compact system needs to be installed for intake into a room. They can filter outside air, providing a cleaner environment, without taking up a lot of space.
These come in small designs intended to be used in electronic equipment, and also come in larger designs that are appropriate for more large-scale operations.
What are Filter Kits?
A filter kit comes with all the various components needed to put together some sort of a filtration system. A kit for an exhaust fan, for instance, may come with the frame, the filter and the fan required to make it all work. This can cut down on costs by including the consumable items—the filter—with the durable components.
Filter kits make installation much easier. A filter kit for a computer case, for instance, would contain the leads, the fan, the filter and the housing for the entire apparatus in a standardized size. This makes it much easier for builders to provide adequate filtration and air flow for their devices.
What are Filter Loss Gauges?
When filters become clogged with debris, they can cause pressure changes in systems that may be detrimental to their function. Filter loss gauges provide a way to measure the pressure drop across a filter, allowing technicians to determine whether or not the filter needs to be changed.
These loss gauges usually have various scales on them that allow the filters to be measured in specific ways. They also oftentimes come with the fittings required to hook them up to systems so that a measurement can be taken.