Although there is no universally accepted method for comparing air-cleaning devices, several investigators of portable air-cleaning units have expressed their results as a ”Clean Air Delivery Rate” or CADR. The CADR is the product of the unit efficiency and the airflow rate, and is a measure of the number of CFM of air it cleans of a specific material.
The DOP Military Standard is the standard set by the federal government to rate particle reduction by HEPA filters. This test rates high-efficiency filters by the percentage of 0.3 micron size particles of dioctylphthalate (DOP) smoke they remove.
HEPA stands for High Efficiency Particulate Arrested Filter, and like the name says, these filters are designed to remove 99.97% of all airborne pollutants 0.3 microns or larger from the air that passes through the filter (these include tobacco smoke, household dust and pollen).
Carbon, the sixth most abundant element in the universe, has been known since ancient times. Many natural substances of base materials are used to make carbon. The most common of these are wood, coal, lignite, and coconut shell. Amorphous carbon is formed when a material containing carbon is burned without enough oxygen for it to burn completely.
ACTIVATED CARBON or AC
Activated carbon is the generic term used to describe a family of carbonaceous adsorbents with a highly crystalline form and extensively developed internal pore structure. Activation creates a fast internal pore network and imparts certain surface chemistries (functional groups) inside each particle. Thus activation gives carbon its unique filtering characteristics.
A pre filter is the primary layer of filtration that collects large particles before they reach the HEPA filter. Eliminating these larger particles, dust and hair extends the life of your HEPA filter. Occasional vacuuming of the exterior of the unit will help extend life of the filters. Frequent pre filter changes will also prolong the HEPA filter life.
When a gas or vapor is brought into contact with a solid, the solid takes up part of it. The molecules that disappear from the gas either enter the inside of the solid, or remain on the outside attached to the surface. The former phenomenon is termed absorption (or dissolution) and the latter adsorption.
There are many simple electronic devices that claim to clean the air in your home by making negative ions and ozone. The claim is accurate–they do make both ozone and negative ions, and they do clean the air in your home. However, that’s not the whole story. First, ozone may have the “fresh” smell that occurs after a thunderstorm (a potent producer of ozone), but ozone is a powerful oxidizing agent and chemical irritant that’s considered an environmental pollutant rather than a charming scent. The manufacturers are taking a nuisance effect and touting it as a “valuable feature.” Second, the negative charges emitted by these electronic devices attach themselves to dust, ash, pollen, and smoke particles and cause those particles to bind themselves to your walls and furniture. The air really does become cleaner, but every surface in your home becomes dirtier as a result.
Ozone, a lung irritant, is produced indirectly by ion generators and some other electronic air cleaners and directly by ozone generators. While indirect ozone production is of concern, there is even greater concern with the direct, and purposeful introduction of a lung irritant into indoor air. There is no difference, despite some marketers’ claims, between ozone in smog outdoors and ozone produced by these devices. Repeated exposure to ozone pollution may cause permanent damage to the lungs. Even when ozone is present in low levels, inhaling it triggers a variety of health problems including chest pains, coughing, nausea, throat irritation, and congestion. It also can worsen bronchitis, heart disease, emphysema, and asthma, and reduce lung capacity.
A micron is a unit of length equal to 1 millionth of a meter or .000039th (39 millionth) of an inch. Another name for micron is micrometer.
Particulate Matter Up to 10 Microns in Diameter (PM10)
The number 10 refers to the particle size measured in microns.
PM 10’s are widely considered the most dangerous to human health.
A standard developed for measuring particulate matter in a pre defined area.
Electrostatic units filter the air using static electricity have a static charge on the filter to allow airborne particles to “stick” to the filter, just like static-charged clothing sticks together.
Ion generators act by charging the particles in a room so that they are attracted to walls, floors, tabletops, draperies, occupants, etc. Abrasion can result in these particles being re-suspended into the air. In some cases these devices contain a collector to attract the charged particles back to the unit. While ion generators may remove small particles (e.g., those in tobacco smoke) from the indoor air, they do not remove gases or odors, and may be relatively ineffective in removing large particles such as pollen and house dust allergens. Although some have suggested that these devices provide a benefit by rectifying a hypothesized ion imbalance, no controlled studies have confirmed this effect.
Moulds produce tiny spores to reproduce, just as plants produce seeds. Mould spores waft through the indoor and outdoor air continually. When mould spores land on a damp spot indoors, they may begin growing and digesting whatever they are growing on in order to survive. There are moulds that can grow on wood, paper, carpet, and foods. When excessive moisture or water accumulates indoors, mould growth will often occur, particularly if the moisture problem remains undiscovered or unaddressed. Moulds can trigger asthma episodes in individuals with an allergic reaction to mould.
An air cleaner must constantly recirculate indoor air in order to effectively reduce concentrations of airborne particulate contamination. Cleaning the total volume of air contained within a room is the equivalent of completely changing the air in that room. Air cleaner filtration capacity is expressed as the number of air changes per hour (ACH). For air cleaners of equivalent filter effectiveness, a higher ACH rating yields higher levels of air quality improvement.