Air Purifiers Introduction: It is hard to imagine today’s world without air purifiers. Air purifiers are needed not just for protection at home and office. Hospitals, defense establishments, nuclear power plants, chemical factories, electronic manufacturing units, research laboratories and some museums – all need air purifiers to guard human/animal/inanimate objects against dangerous air pollutants.
The US Environment Protection Agency (EPA) has observed that most houses and a great number of offices need air purifiers/cleaners/filters, or they can have their central AC systems equipped with air filtration because the quality of air indoors has come down in recent years, making it 2 – 5 times more polluted than air outdoors. Dust, pet hair, pollen, cigarette smoke and fibers can cause headache, breathing problems and other health issues.
Air purifiers are designed: • to remove pollutants from the air you (or animals) breathe, improving health and quality of life. • to protect inanimate objects from getting damaged. These can be computer/electronic components, medicines or treasured relics/documents in museums, etc.
Some air purification/cleaning devices are designed to be installed in the ducts of your central heating and air-conditioning (HVAC) system at home. These clean the air in your entire house. For cleaning selected areas or rooms, you can use portable room air cleaners.
Types of Air-contaminants/Pollutants Air can be contaminated/polluted by allergens, viruses, bacteria, chemicals, radiation or odors. Every one of these can pose a health problem for human/animal life, highly sophisticated electronic components, pharmaceuticals, or highly treasured objects such as documents/museum exhibits, etc.
Categories of Air-Purifiers/Filters? Air-purifiers are divided into several categories, depending on what they eliminate from air: allergens, bacteria, viruses, radioactive particles, smoke, odors and chemical particles. Depending on the nature and size of the contaminant/pollutant involved, you can select an Air-Purifiers/Filter from the following categories:
Mechanical Filters make air pass through a special screen that traps all allergens, and even tobacco smoke. HEPA filters are the most well-known mechanical filters. Most HEPA air filters/purifiers claim an efficiency of 99.97% in removing particles of 0.3 microns diameter. HEPA products are endorsed by doctors for alleviating asthma/allergy symptoms of patients.
Electronic Air Purifiers/Cleaners: Electronic/Electrostatic Precipitators trap allergens by passing them through an electric field, and directly charging them. They are later trapped using oppositely charged plates. These are the most efficient filters, especially those that run on fans. However, they need regular maintenance.
Ionic Precipitators/Ionizers (aka Negative Ion Filters) release ions into the surrounding air, unlike electronic precipitators, which draw the particles in, and then charge them directly, the released ions get attached to the airborne contaminants, and charge them. The charged particles get attracted and cling to curtains and walls, or fall to the floor.
Both electronic air cleaners (Electronic Precipitators and Ionizers) are effective only when combined with other air-filtering mechanisms as they target only particles, not gases and VOC. *Note: If you plan to buy an electronic air-purifier, make sure it does not produce ozone.
Hybrid Filters use a combination of both mechanical and electrostatic components.
Gas Phase Filters strictly remove odors/gases such as cooking gas, methane/hydrogen sulfide (in mines), etc. They do not eliminate allergens.
Ozone Generating Air-Purifiers are operated on the claim that ozone cleans the air. However, they are not endorsed by the EPA or ALA as healthy air-concentrations of ozone have little effect on indoor air pollutants, and if ozone levels are increased, they can be harmful to public health. Therefore, manufacturer-claims of safe ozone levels are rather hype.
Activated Carbon Filters change contaminants from gaseous to a solid particles and eliminates them. Activated carbon is porous, and adsorbs volatile chemicals molecular in size, but cannot remove larger particles.
Ultra-Violet Ray (UV) Filters are classified as “Ultraviolet Germicidal Irradiation Cleaners” (germicidal means germ-killing) by the EPA. They are high frequency and low wave-length rays that directly kill living organisms such as bacteria and viruses. However, they have no effect on gaseous VOC or dust particles and mite allergens. They are usually fitted as complementary filters to aid HEPA filters.
Cleanroom Filtration is to clean air in large interiors such as huge building, offices and factories. Most modern computer and electronic components get damaged by the tiniest of dust particles. Hence, computer/electronic/medical manufacturing companies test sensitive computer/electronic components, sterile medical equipment, semi-conductors, etc. in the purified, sterile atmosphere created by Cleanrooms. You can eliminate almost 100% of air contaminants. Cleanrooms are also indispensable in chemical, pharmaceutical and bio-technology industries. A Cleanroom filtration is complex, involving air flow & pressure, filtration and special clothing for workers.
EMF Filters incorporate a very recent technology called Enhanced Media Filtration (EMF), developed by the US military. They have overtaken HEPA as the overall leader in effective air filtration. This technology has sprung up in response to the threat of terrorism/germ warfare. Over time, it has been adapted to manufacturing environments/processes, where a sterile, particle-free room is vital. Currently, there are a few companies that have combined the best air filtration advances with EMF technology.
Aquasana, for example, has obtained the patent for an EMF system called the Health-Air Deluxe Air Purifier, which meets the standards of an FDA regulatory Class II Medical Device, which in turn means, it can be used for removal of particles in the air at home for health and medical purposes.
Which Air-Purifier/Filter is Suitable for me? In today’s competitive market, air-purifiers are designed with not just one category of air-filter system, but multiple air cleaning systems, in order to handle most of the pollutants/contaminants. Allergies are caused by various types of particles (allergens) suspended in air.
For allergies caused by pollen and larger particles (0.3 micron upwards), near/true HEPA air purifiers, and some Ionic (precipitators) air cleaners are enough for effective air-purification.
However, if more than 90% of particulates are 0.3 microns and smaller in size including: viruses, some microorganisms (bacteria, viruses and germs), dust, and allergens from mites and pet (cats, dogs, raccoons, etc) dander/hair, you need ionizers/ionic precipitators, activated carbon filters, or UV filters in addition to mechanical HEPA filters.
For even smaller particles in soot, smoke and smog, you need air-purifiers with activated charcoal filters, and some types of ozone generators.
Air-Purifier Abbreviations/Acronyms EPA (Environmental Protection Agency) NRDC (Natural Resources Defense Council) AAFA (Asthma and Allergy Foundation of America) UVGI (Ultra Violet Germicidal Irradiation) technology is used to sanitize air, water or transparent materials/surfaces. PCO (Photo-Catalytic Oxidation) comprises of a UV lamp along with a catalyst that reacts with light, and destroys only gaseous pollutants by converting them into harmless products. MERV (Minimum Efficiency Reporting Value) ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) AHAM Association of Home Appliance Manufacturers HEPA (High-Efficiency Particulate Air/Accumulator) HEGA (High Efficiency Gas Adsorbers) CADR (Clean Air Deliver Report) HVAC system (Heating, Ventilation, and Air-Conditioning system)
CADR: AHAM Capacity Certification: AHAM performs testing and certification of air-purifiers/cleaners and other home appliances. AHAM also publishes CADR, which is the volume of air that an air purifier cleanses a particular pollutant, and is measured in cubic feet per minute. An air-cleaner is ranked/rated for its effectiveness at removing airborne particulates such as dust, pollen and smoke. AHAM’s CADR range from 10 to 400 for dust, 10 to 450 for tobacco smoke, and 25 to 450 for pollen, with scores above 350 considered excellent and those below 100, poor. The AHAM spec is accepted by the American National Standards Institute (ANSI).
AHAM MERV Certification: This AHAM certification is for MERV or minimum efficiency of the filter system. A 16 MERV rating is the maximum. Reliable air-purifiers must have at least a MERV 10.