What is the required flow rate for Andersen N6?

• A. 15 lpm
• B. 20 lpm
• C. 30 lpm
• D. 28.3 lpm

Answer: (D)

The main idea is that the Andersen N6 must be operated at a precise sampling flow so the cascade impactor’s stages can accurately separate particles by size. Each stage’s aerodynamic cutoff is defined for a specific flow, and for the six-stage Andersen impactor the designated flow is 28.3 liters per minute (about 1 cubic foot per minute at standard conditions). Keeping this flow ensures the particles are collected on the correct stages with the intended size ranges; if the flow deviates, the cutoffs shift and the size distribution data become biased or inconsistent. In practice, you verify and maintain this flow with a calibrated flowmeter and account for temperature and pressure to standardize measurements.