The Personal Environmental Monitor (PEM) is a small, lightweight, personal sampling device consisting of a single-stage impactor and an after-filter. Aerosol particles are sampled through the single-stage impactor to remove particles above the 50% cut-point of either 2.5 or 10 µm in aerodynamic diameter. These large particles are collected on a greased ring and are discarded after sampling. Particles smaller than the 50% cut-point pass through the impactor and are collected on a 37-mm after-filter. To determine personal exposure, the filter may be analyzed gravimetrically for particle mass and chemically for specific chemical compounds. A personal air sampling pump provides the necessary airflow through the PEM. Use the PEM for air pollution studies, indoor air quality assessments, and personal sampling for industrial hygiene applications (not an EPA reference method for ambient air).
The PEM operates on the principal of inertial separation of airborne particles using an impactor. Particle-laden air is accelerated into the sampler through the round nozzles located in a circle around the outer edge of the cover. The exiting airstreams impinge upon an impaction ring. Due to inertia, the larger particles cross the airstreams, impact, and are retained on the ring. The smaller particles are carried along the airstreams flowing around the ring and are collected on the after-filter. Oil must be applied to the impaction ring to keep particles from bouncing off this surface. Any type of oil can be used including olive oil, machine oil, vegetable oil, and silicone grease.