HEPA filters known as High-Efficiency Particulate Arrestance filters were originally developed to filter fine radioactive particles. A HEPA filter will filter with a minimum efficiency 99.95% of particles 0.3 microns and 95% of particles 0.1 microns. With 1 micron measuring just 1/10,000 of a centimeter and the smallest particle visible to the naked eye being 40 microns. 0.3 microns is many times smaller than dust mites, mold spores, pet allergens and pollens. HEPA filters are widely used in medical applications including: clean rooms, pharmaceutical manufacturing and any environment where clean or sterile conditions are required. 

Medical grade HEPA filters are made from highly efficient filter paper. The paper is folded in a concertina configuration to maximize the surface area of the filter and allow air to flow through with minimal resistance. There is a certain ratio of filter paper to airflow volume which must be followed in the construction of the filter to achieve the 99.97% efficiency rating. If there is not enough filter paper, efficiency will not be to HEPA standards. 


How are Inova Purifiers HEPA filters made?


The filter paper is bonded airtight inside a filter casing made from steel. HEPA filters are delicate, they cannot be vacuumed or cleaned but due to the considerable surface area of the filter paper they will generally last 3 years or more when used with proper pre-filtration. HEPA filters must also have an airtight seal or gasket on the external face to prevent air from bypassing around the filter. 

Air bypass is a common problem with air purifiers, due to lack of a proper seal or filters are made from less than ideal sealing materials such as cardboard, paper or plastic. Air bypasses around the filter resulting in efficiency being a fraction of the stated 99.95%. All Inova Purifiers HEPA air purifiers are factory certified to filter 99.99% @ 0.3 microns efficiency. 

NB: Most residential HEPA air purifiers sold in America do not conform to medical grade HEPA standards. There is no regulatory authority which monitors claims by manufacturers that HEPA filters sold in either vacuum cleaners or air purifiers are actually 99.95% efficient.


Most people purchase air purifiers to remove dust and allergens from the air and want the highest level of efficiency available. Medical-grade HEPA filters offer the highest level of efficiency: a minimum capture of 99.99% of particles at 0.3 microns in size and larger. With 1 micron measuring just 1/10,000 of a centimeter HEPA filters will remove dust mites, mold spores, pet allergens, pollens and ultra fine particles from the air.

Medical-grade HEPA filers are made from a very fine paper (not polypropylene or synthetic materials) which traps microscopic particles so fine they will even remove bacteria and viruses. This is why HEPA filters are used in hospital and medical applications, including operating theaters.

With the rise in popularity of HEPA vacuum cleaners and air purifiers, many manufacturers are claiming to use HEPA filters, however the majority of these are not Medical-grade and when tested, fail to filter 99.99% @ 0.3 microns of particles from the air. If you suffer from allergies or asthma it is critical to use an air purifier with a medical-grade HEPA filter.