Performance of an omni-directional sampling system for ambient aerosol measurement with active sampling devices

摘要

Ambient aerosol measurement by active sampling instruments can easily be affected by an external air movement.Due to inertial effects in e.g.health related sampling for particles of interest,such as inhalable,or PM-fractions,a non-representative sampling conditions may occur.This may happen when an inlet into an instrument is oriented at an angle with respect to the prevailing direction of the air movement.A satisfactory but impractical solution to this problem,especially in environmental monitoring,is an isokinetic sampling probe.An alternative,practical approach is an inlet system allowing sampling independent of direction in a horizontal plane - the omni-directional sampling system.The system described here (Fig.1) consists of a sampling head with flow steering channel,followed by an aerosol transfer tube which connects to an active particle sampling and sizing device - a cascade virtual impactor.