HEPA filters are used in various clean air environments and their primary function is to remove fine particulates from the air.
These particulates could be unwanted chemicals during chemical reaction testing, airborne contaminants during production or airborne particulates that could cause harm to human health.
It is, therefore, crucial that the HEPA filters are tested and maintained to ensure their optimal function in every application.
HEPA filters protect people and the environment from harmful airborne substances and are most commonly used in clean rooms and laboratories. However, they are also used in hospital theatre rooms, manufacturing facilities, patient isolation rooms and the optical and electrical industries.
These filters are designed to remove all airborne particles with the Most Penetrating Particle Size (MPPS) being 0.3 microns (0.0003mm) in diameter, providing air efficiency of 99.97%.
Particles above and below the MPPS, increase towards 100% removal, the larger particles being mainly removed by inertial impaction and interception, and the smaller particles by diffusion.
Dispersed oil particulate (DOP) testing is the process of manually introducing particulates into the HEPA filter and measuring the percentage of bypass at the output.
This is also known as a HEPA filter integrity test as it tests the integrity of the filter and the housing.
A DOP test is done by allowing oil to be dispersed through an aerosol spray into the upstream flow of the filter while the number of particles in the downstream flow is measured.
In order to measure the output, the operator uses a calibrated photometer which allows for the measurement of the concentration of particles in the air.
To obtain the results, the measurements of both the upstream and downstream air are compared with one another to determine the level of penetration of the particulate through the filter and its housing.
These results provide a clear indication of the integrity of the filter and whether it is providing the correct standard of clean air for its application.
The physical location of the HEPA filter as well as the type of application will determine how often DOP testing is necessary.
However, every time the filter is moved to a new location or changed out, a DOP test should be done to ensure no damage was done to the unit during transportation or filter replacement.
In addition, it is advised to carry out DOP testing after any maintenance has been done on the filter and its housing. Testing should also be done every time a new project is started.
Furthermore, as a general rule, DOP testing should be done every 2 years and the results must be kept on site for quality assurance testing and auditing processes.
DOP testing is a crucial part of ensuring and maintaining the integrity of HEPA filters and the quality of the clean air in the room.
High quality clean air is non-negotiable in clean air environments as this is what protects the occupant, product and environment from harmful chemicals or substances.
To find out more about the importance of DOP testing your HEPA filters and housings, or to learn more about our clean air equipment, contact us.
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