A brief description of common problems in the use of high efficiency filters

I. Aerosol occurrence problems

High-efficiency air filters use on occasions with high requirements, so for all products using the method of inspection by the unit is very important, should use easy to penetrate the tiny particles for detection, so that the test results have practical significance, the filtering mechanism is mainly the following four effects:

1. Inertial collision.

2. Direct retention.

3. Gravitational sedimentation.

4. Diffusion effect.

II. Concentration detection problem

The concentration of particles after filtration of high-efficiency air filters is very low, so the method of "sampling-weighing" is very difficult to measure, so the more commonly used light scattering method, flame photometric method, particle counting method, and other methods.

III. D.O.P method

This is a commonly used method, the aerosol used is dioctyl phthalate, a colorless and transparent liquid, the method is to heat the colorless and transparent liquid D.O.P under certain conditions, vapor, and then mix it with cold air so that it condenses into a monodisperse phase of 0.3pm droplets, which becomes the experimental aerosol.

IV. Sodium flame method

The test particles for this method are small solid crystals of Nacl. 2% aqueous NaC1 is sprayed and mixed with a dry air phase so that the water in the droplets evaporates to form NaC1/J crystals with a particle diameter of approximately 0.02 - 2 pm. This method was initially used as a standard for testing gas masks.