Pressure-based airflow sensing in particle impactor systems

A method of measuring a volumetric flow rate of a fluid flow through a particle impactor system, the method comprising the steps of:

• pulling said fluid through a plurality of intake apertures of a sampling head of said particle impactor system, wherein said fluid contains a plurality of particles;
• pulling said fluid past an impact surface positioned in fluid communication with each of said plurality of intake apertures, causing a change in direction of said fluid, whereby at least a portion of the particles are directed onto said impact surface for collection;
• determining a flow rate of said fluid;
• determining ambient pressure;
• and
• determining said volumetric flow rate as a function of said flow rate of said fluid and said ambient pressure.

A particle impactor system comprising:

• a sampling head having a plurality of intake apertures;
• an impact surface positioned in fluid communication with each of said plurality of intake apertures;
• an impactor base supporting said impact surface, wherein said impactor base comprises a fluid outlet, wherein said sampling head and said impactor base together form a fluid tight seal such that fluid can only flow into or out of said particle impactor system through said plurality of intake apertures and said fluid outlet;
• a flow restriction positioned in fluid communication with said plurality of intake apertures, said fluid outlet or both said plurality of intake apertures and said fluid outlet;
• first pressure sensor comprising a differential pressure sensor positioned to measure a differential pressure across said restriction;
• and
• a second pressure sensor positioned to measure an ambient pressure inside or outside of said system.