Which air filter is right for your
by Stephanie Earley, the marketing manager of filtration
products for the Kimberly-Clark Corporation,
Good indoor air quality (IAQ) depends on a number of factors, including
effective filtration, which provides the primary defense for building
occupants and HVAC equipment against particular pollutants.
Today’s higher standards in filtration, coupled with rigorous attention
to filter selection and maintenance, helps to produce cleaner, purer air and
reduce IAQ problems.
Which HVAC filter is right for you?
Various particle sizes will cause different types of problems: Facility
managers should work to identify the types and sizes of particular
pollutants in their buildings to determine the best type of HVAC filter for
Selecting HVAC filters based on the needs of the facility instead of
simply their initial costs will lead to a review of filter efficiency as a
determining factor. Filtration efficiency defines how well the filter will
- Low-efficiency filters are typically used to keep lint and dust from
clogging the heating and cooling coils of an HVAC system.
- Medium- and high-efficiency filters are typically used to remove
bacteria, pollen, soot and other small particulates.
Initial and sustained efficiency are the primary performance indicators
for HVAC filters.
- Initial efficiency refers to the filter’s efficiency “out-of-the-box.”
- Sustained efficiency refers to efficiency levels maintained throughout
the service life of the filter.
Some filters have lower initial efficiency and do not achieve high
efficiency until a “dirt cake” has built up on the filter – typically after
30 days. Other filters offer both high initial as well as sustained
efficiency, meaning they achieve an ideal performance level early and
maintain that performance level.
The American Society of Heating, Refrigerating, and Air-Conditioning
Engineers (ASHRAE) developed two HVAC industry standards that address the
efficiency issue: ASHRAE 52.1 and ASHRAE 52.2.
ASHRAE 52.1 measures:
- Pressure drop – how the filter affects air flow and energy costs. A
low pressure drop typically translates into higher energy efficiency. A
high pressure drop means reduced air flow to the HVAC unit, requiring more
energy to operate the unit.
- Arrestance – the amount of synthetic dust a filter is able to capture.
- Dust spot efficiency – a measure of the ability of the filter to
remove atmospheric dust from the test air.
- Dust holding capacity – the amount of dust a filter can hold until a
specified pressure drop is reached. Higher capacity means a longer filter
life. (When evaluating dust holding capacity, it’s important to compare
dust holding capacities between filters at the same final pressure drops
to make accurate comparisons of projected filter life.)
The ASHRAE 52.2 Standard measures the fractional particle size efficiency
(PSE) of an HVAC filter, which indicates the filter’s ability to remove
airborne particles between 0.3 and 10 microns in diameter.
A Minimum Efficiency Reporting Value (MERV) rating is assigned to the
filter media depending on the PSE in three different particle size ranges
(0.3 to 1 micrometer, 1 to 3 micrometers, and 3 to 10 micrometers).
MERV is a numerical system of rating filters based on a minimum particle
size efficiency. A rating of 1 is least efficient, while a rating of 16 is
most efficient. Lower ratings typically reflect a more cost-conscious
In addition to the performance factors measured under ASHRAE 52.1 and
52.2, consider these additional variables when selecting a filter:
- Moisture resistance – how high humidity and moisture affect the
- Temperature limitations – how the filter performs at application
- Flammability – how the filter performs in flammability tests. Check to
see if UL Class I or Class II rated filters are needed to conform to local
Environmental Marketing Ideas
Hygienists Resources |
Air-Pollution-Genetics | Office-Germs |
Smoking-Causes-Asthma | Road-Dust-Mold
| Home-Pesticide-Hazard |
| Traffic-Heart-Attack |
Respiratory-Infection | OSHA-Compliance-Tips
| Indoor-Pollution-Hazards |