*4.2.1 Flat fiberglass filters*

*Low-temperature Technologies*

**Table 2.**

**Example particle Size (μm)** Hair 20–200 Pollen 10–100 Spores 10–25 Toner 5–20 Oil fog 0.3–5 Bacteria 0.2–25 Tobacco smoke 0.01–1 Virus 0.002–0.05

*Particle size ranges of common pollutants specified by Standard 52.2.*

Unfortunately, filters that use the principle of electrostatic attraction can "fool" the test by providing a high MERV during tests. However, due to the loss of electrostatic attraction during operation, a much lower value is obtained during application. Hence, the user may not be getting the particle removal efficiency that they

Multiple studies have shown that coarse-fiber media (charged synthetic media), unlike fine-fiber media (fiberglass media), perform differently in real-life applications. Coarse-fiber media depends on an electrostatic charge to achieve the published filter efficiency. When atmospheric air, in which 99% of the particulate matter less than 1.0 micron in size, passes through a filter, the very fine particulate

Qian [23] isolated Streptophyta from dust samples collected from the filters of air-conditioning systems at a rate of 45%, whereas the rate in the indoor air was found to be only 2.4%, which provides an indication of the efficiency of HVAC filter

matter will dissipate the charge, and the filter rapidly loses efficiency.

There are six types of filters, which are briefly described below.

systems (preventing particles sizes that are larger than 3 μm).

**4.2 Types of most common HVAC filters**

**186**

originally specified.

*How to read an ASHRAE 52.2-2007 test report.*

**Figure 7.**

The main advantage of fiberglass filters is they are very cheap, easy to install, and readily available in stores. Accordingly, although they have a lifespan of only 1 month, replacing them on a monthly basis would not pose an inordinate financial burden. Unfortunately, they are not particularly effective in terms of trapping particles.
