China's existing standard notation and foreign counting method, the main difference is that:
1. The domestic only measure new filter efficiency, foreign send dust measuring efficiency in different stages of the average;
2. Domestic measurement is greater than a certain size particle filtration efficiency, all foreign measure the efficiency of the particle size;
3. The foreign count measurement using standard artificial dust, domestic use of atmospheric dust.
2.2.2 hepa filter
GB13554-92 national standard, high efficiency filter as follows:
1. According to provisions of GB6165 test sodium flame method, the efficiency of 99.9% or more filter;
2. The particle size of 0.1 mm or more particles, the efficiency of 99.999% or more filters.
The former refers to the general high efficiency filter, by contrast, foreign generally define efficiency and high efficiency filter is 99.97% or greater. The latter refers to the ultra high efficiency filter.