2020-08-18

National cleanroom air filter standards and classification instruction

Determining Air Filter Efficiency and Configuration for Cleanroom Air Filter Standards

Selecting the appropriate air filter configuration for cleanrooms requires strict adherence to purification standards. The efficiency of the final-stage air filter must align with the cleanroom’s classification, while earlier-stage filters must be chosen to protect downstream stages and optimize system performance. Below is a structured guide to filter selection, efficiency standards, and operational considerations.

1. Filter Efficiency Classification & Selection Criteria

Cleanroom requirements dictate the number of filtration stages and their respective efficiencies:

General Purification: Single-stage primary filter (efficiency ≥20% for particles ≥5 μm).
Medium Purification: Two-stage system (primary + medium-efficiency filters; ≥20% for ≥5 μm and ≥20% for ≥1 μm).
Ultra-Clean Purification: Three-stage system (primary + medium + high-efficiency filters; ≥20% for ≥5 μm, ≥70% for ≥1 μm, and ≥99.99% for ≥0.5 μm).

Adjacent filter stages must have compatible efficiency gradients to ensure progressive particle removal. A significant disparity between stages may render upstream filters ineffective, compromising downstream HEPA filters.

2. Efficiency Standards & International Equivalents

Chinese Standards (GB/T14295-93 & GB13554-92)

Filter Type	Particle Size Target	Filtration Efficiency (E)	Initial Resistance (Pa)
Primary	≥5 μm	80 > E ≥ 20	≤50
Medium-Efficiency	≥1 μm	70 > E ≥ 20	≤80
High-Efficiency	≥1 μm	99 > E ≥ 70	≤100
Sub-High Efficiency	≥0.5 μm	E ≥ 95	≤120
HEPA	≥0.5 μm	E ≥ 99.99	≤220
Ultra-High Efficiency	≥0.1 μm	E ≥ 99.999	≤280