Things decay: either they wear off or fall apart. Things emit: whether from natural sources like wildfires or volcanoes, or man-made sources like vehicles and factories. And things get blown away: like dust from road-sides or barren fields, or pollens from flowers in blooms. In all these cases, fine particulate matter—sometimes too fine to be seen by the naked eye—get added to air and cause all kinds of health issues.
While the above-mentioned problem of particulate matter is bad enough outdoors, domestic activities—like cooking, burning, etc.—add to the problem indoors.
Obviously, the smaller the particle, the greater is the impact on the body. The human nose and throat are capable of arresting particulate matter up to a particular size. But any smaller, these fine particulates pass into the respiratory system and finally into the blood stream, causing great harm.
Particulate matter is best understood in comparison to a human hair. The width of a human hair is about 100 microns (micrometers). Particles that are 10 microns or less in diameter are termed PM 10. Particles of size 2.5 microns or less are termed PM 2.5, and particles of 1 micron or less are called PM 1.0.
Comparison chart of human hair size with Particulate Matter
Impacts of PM 2.5
Long-term exposure to PM 2.5—and PM 1.0—significantly increases chances of cardiopulmonary problems. WHO estimates that around 7 million people die every year from exposure to fine particles in polluted air that lead to diseases such as stroke, heart disease, lung cancer, chronic obstructive pulmonary diseases and respiratory infections, including pneumonia.
On the other hand, a study conducted in the US between 2000 and 2007 found that the average life span gets extended by 0.35 years for every 10 µg/m3 decrease of PM2.5.
Filtration of Particulate Matter
Particulate matter is best controlled by using mechanical or electrostatic filters.
- Mechanical Filters
A mechanical filter is a screen of dense synthetic fibre, enclosed in a frame, through which air is made to pass. While the air passes, the fibres trap the dust and debris. Mechanical filters are commercially available in 4 types:
- Coarse filters
- Fine filters
- HEPA filters
- ULPA filters
The table below gives the US (ASHRAE & IEST) and European Union classification of air filters:
| Table for Air Filters and Efficiency | |||||
| Classification | US ASHRAE 52.2 | European Union EN779 Class | Typical Controlled Contaminant | Application | |
| Pre Filter (G Class) | MERV 1 | G1 | Particle bigger than 10.0µm: Pollen, Spanish Moss, Dust Mites, Sanding Dust, Spray Paint Dust, Textile fibres, | Gross Filter, Domestic and Commercial | |
| MERV2 | G2 | ||||
| MERV 3 | |||||
| MERV 4 | |||||
| MERV 5 | G3 | Particle size within 3.0µm-10.0µm: Mould, Spores, Hair Spray, Cement Dust, Snuff, Powdered Milk | Commercial Industrial, Paint Shop | ||
| MERV 6 | |||||
| MERV 7 | G4 | ||||
| MERV 8 | |||||
| Medium Filter (F Class) | MERV 9 | F5 | Particle size within 1.0µm-3.0µm: Lead dust, Milled Flour, Coal Dust, Auto Emissions, Nebulizer Drop, Welding Fumes | IAQ Concerned commercial & industrial, medical | |
| MERV 10 | |||||
| MERV 11 | F6 | ||||
| MERV 12 | |||||
| MERV 13 | F7 | Particle size within 03.µm-1.0µm: All Bacteria, Cooking Oil, Most Smoke, Copier Toner, Most Face Powder, Most Paint Pigments | IAQ Concerned commercial & industrial, medical, food, etc. | ||
| MERV 14 | F8 | ||||
| MERV 15 | F9 | ||||
| MERV 16 | |||||
| Table for Air Filters and Efficiency (HEPA and ULPA Filters) | |||||
| Classification | IEST RP-CC001.3 | European Union EN1822 Class | Typical Controlled Contaminant | Application | |
| HEPA Filter (H Class) | N/A | H10 | Particle size bigger than 0.3µm: Virus (unattached), Carbon Dust, Sea Salt, All Combustion Smoke. Radon Progeny | All Types of Cleanrooms | |
| H11 | |||||
| Type A | |||||
| Type C | H12 | ||||
| H13 | |||||
| Type D | H14 | ||||
| ULPA Filter (U Class) | Type F | U15 | Particle size bigger than 0.12µm | Super Cleanroom | |
| U16 | |||||
| U17 | |||||
Note:
1. ASRAE: American Society of Heating Refrigerating & Air-Conditioning Engineers
2. MERV: Minimum Efficiency Reporting Value
3. HEPA: High Efficiency Particulate Arrester/Air Filter
4. ULPA: Ultra Low Penetration Air Filter
5. IEST: Institute of Environmental Sciences and Technology
- Electrostatic Filters
Unlike a mechanical filter that puts a physical roadblock to the flowing air, an electrostatic precipitator (ESP)—commonly called an electrostatic filter—is a non-blocking technology. As the air flows through the casing, the ESP charges the particulate matter, which then get drawn to oppositely-charged collector plates. Many ventilation systems—where the focus is on optimizing air flow—use electrostatic filters to achieve high-quality air filtration.
