How to Breathe Healthier Air-HEPA Filter and UV Lamp is Key

As you know,?#HEPAFilter?is the most important part of the air purifier, and The level of HEPA Filter determines the efficiency of filtration.

Do you know why?#HEPA?effects are measured in 0.3 microns particles instead of 0.1 microns?In fact, PM0.3 microns is easier to break through the protection of the HEPA filter because it is less susceptible to van der Waals forces. Therefore, if the HEPA filter has a filtration effect of #99，97% on PM0.3 microns, the filtration effect on PM0.1 microns can even reach #99，997%. So, the HEPA filter that can filter PM0.1microns is not necessarily the best.

Common standards require that a HEPA air filter must remove—from the air that passes through—at least 99.95% (ISO, European Standard) or 99.97% (ASME, U.S. DOE) of particles whose diameter is equal to 0.3 microns,?with the filtration efficiency increasing for particle diameters both less than and greater than 0.3 microns.(Below pictures will help you understand better).??HEPA filters capture pollen, dirt, dust, moisture, bacteria (0.2-2.0 microns), virus (0.02-0.3 microns), and submicron liquid aerosol (0.02-0.5 microns). Some microorganisms, for example, Aspergillus niger, Penicillium citrinum, Staphylococcus epidermidis, and Bacillus subtilis are captured by HEPA filters with photocatalytic oxidation (PCO). HEPA is also able to capture some viruses and bacteria which are ≤0.3 microns. HEPA is also able to capture floor dust which contains Bacteroidia, Clostridia, and Bacilli.

Mechanism

HEPA filters are composed of a mat of randomly arranged fibers. The fibers are typically composed of polypropylene or fiberglass with diameters between 0.5 and 2.0 micrometers. Most of the time, these filters are composed of tangled bundles of fine fibers. These fibers create a narrow convoluted pathway through which air passes. When the largest particles are passing through this pathway, the bundles of fibers behave like a kitchen sieve which physically blocks the particles from passing through. However, when smaller particles pass with the air, as the air twists and turns, the smaller particles cannot keep up with the motion of the air and thus they collide with the fibers. The smallest particles have very little inertia and they always move around the air molecules like they are bombarded by these molecules (Brownian motion). Because of their movement, they end up crashing into the fibers. Key factors affecting its functions are fiber diameter, filter thickness, and face velocity. The air space between HEPA filter fibers is typically much greater than 0.3 μm. HEPA filters in very high level for smallest particulate matter. Unlike sieves or membrane filters, where particles smaller than openings or pores can pass through, HEPA filters are designed to target a range of particle sizes. These particles are trapped (they stick to a fiber) through a combination of the following three mechanisms:

1. Diffusion: Particles below 0.3 μm are captured by diffusion in a HEPA filter. This mechanism is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 μm in diameter. The small particles are effectively blown or bounced around and collide with the filter media fibers. This behavior is similar to Brownian motion and raises the probability that a particle will be stopped by either interception or impaction; this mechanism becomes dominant at lower airflow.
2. Interception: Particles following a line of flow in the air stream come within one radius of a fiber and adhere to it. Mid size particles are being captured by this process.
3. Impaction: Larger particles are unable to avoid fibers by following the curving contours of the air stream and are forced to embed in one of them directly; this effect increases with diminishing fiber separation and higher air flow velocity.

UV-C lamp

The HEPA Filter is responsible for intercepting particulate matter, while the UV lamp is mainly responsible for killing viruses and bacteria.

There are mainly three types of UV lamps: UV-A, UV-B and UV-C, among which UVC Lamp is mainly used for disinfection.Generally speaking, in air purifiers, UV lamps are often used with photocatalyst filters.

Using a catalytic chemical reaction from titanium dioxide and UVC exposure, oxidation of organic matter converts pathogens, pollens, and mold spores into harmless inert byproducts. However, the reaction of titanium dioxide and UVC is not a straight path. Several hundreds of reactions occur prior to the inert byproducts stage and can hinder the resulting reaction creating formaldehyde, aldehyde, and other VOC's en route to a final stage. Thus, the use of titanium dioxide and UVC requires very specific parameters for a successful outcome. The cleansing mechanism of UV is a photochemical process. Contaminants in the indoor environment are almost entirely organic carbon-based compounds, which break down when exposed to high-intensity UV at 240 to 280 nm. Short-wave ultraviolet radiation can destroy DNA in living microorganisms. UVC's effectiveness is directly related to intensity and exposure time.

UV has also been shown to reduce gaseous contaminants such as carbon monoxide and VOCs.UV lamps radiating at 184 and 254 nm can remove low concentrations of hydrocarbons and carbon monoxide if the air is recycled between the room and the lamp chamber. This arrangement prevents the introduction of ozone into the treated air. Likewise, air may be treated by passing by a single UV source operating at 184 nm and passed over iron pentaoxide to remove the ozone produced by the UV lamp.

If you want to breathe cleaner air, you can choose an air purifier with HEPA filter and UV lamp, which can keep you healthy.