About HVAC filters:

• HVAC stands for heating, ventilating, and air conditioning.
• The HVAC systems are used in industries, commercial and residential buildings where humidity and temperature need to be closely regulated.
• The filtration systems in general can be classified as
• Liquid -Solid separation (e.g. vacuum and pressure filters),
• Air-Gas separation (e.g. activated carbon filters) and
• Air-Solid separation (i.e. filters that remove particulate matter from air).
• HVAC filters belong to the category of air filtration products.
• The filtration products are also classified based on their end application as depicted below:

• The HVAC filters include pre filters, medium efficiency filters and HEPA filters.
• HEPA or High Efficiency Particulate Air filters are high efficiency filters capable of removing 99.97% of airborne particles of 0.3 micrometers (μm) diameter.
• Filters capable of removing 99.999% of dust, pollen, mold, bacteria and any airborne particles of size 120 nanometres or larger from the air are categorized as ULPA or Ultra Low Penetration Air filter.

Product Characteristics:

• Filter media used in air filters are nonwoven fabrics laid perpendicular to the air flow to arrest the solid particulate matter.
• Air filters can be either mechanical filters or electrostatic filters (electro statically enhanced filters).
• Most of the filters fall under the category of mechanical filters and depend on four primary filtration mechanisms –
• Sieving,
• Impaction,
• Interception, and
• Diffusion.
• Filters are characterized by their
• Filtration efficiency,
• Merv rating and
• Micron size.

• Filtration efficiency: Filtration efficiency can be calculated using the following formula

                  Filter Efficiency = 1 – [Particles Downstream/ Particles Upstream]
                                    

• MERV Ratingor Minimum Efficiency Reporting Value is a number from 1 to 16 that is relative to an air filter‘s efficiency. The higher the MERV, the more efficient the air filter is. A higher MERV creates more resistance to airflow because the filter media becomes denser as efficiency increases. The table below gives the application areas of various types of filters.

• Micron size: The micron size is indicative of the size of particles which can be removed by a particular type of filter. Based on this filters can be classified as follows:

Raw materials:

• The major filter media used in HVAC filters are nonwoven and made of polyester, polypropylene and glass fibre.
• These nonwoven media are generally needle punched and have a GSM of 200-250.

Technology used:

• Weaving
• Nonwoven needle punching