Experimental investigation of the contaminated volume around a person in a clean room

Abstract

To monitor the particle concentration in a clean room, the measuring position is usually chosen based on a risk analysis and a monitoring plan. The demand zone is the area on the table, where the product is placed and where very clean air must be assured. Measuring the particle concentration in this working area is often difficult, as the measuring probe may obstruct the work flow. A situation that frequently occurs in a clean room is that of a person working at a work table. In this experimental investigation, the radial spread of particles, emitted by a dummy, is investigated. Particles are emitted from the proximity of the mouth region, with a source strength that is much higher than the normal particle emission of a human being when speaking. The aerosol distribution is measured with a laser particle counter at varying measuring positions. In the present case, the demand zone is defined as the area above the table in front of which the dummy is standing, 250 mm deep and 500 mm wide. Hot-wire anemometers are used to measure the velocity profile in the close up range of the dummy. The influence of the distance between table and wall on the velocity and particle field is investigated, at varying inlet airflow velocities between 0.25 - 0.45 m/s. The results show that the table positioning has an influence on the flow velocities in the demand zone and that the table should be positioned in the room if possible.