Abstract: Disclosed is an in-line silencer for a clean room breathing apparatus which reduces noise transmitted to a user from an attached air blower. The clean room breathing apparatus includes a headgear assembly worn by the user and an air blower that supplies air to or exhausts air from the headgear assembly through a connecting air hose. The in-line silencer is installed in the air duct between the air blower and the headgear assembly. The silencer has a shell housing with couplings at opposite ends for attaching the silencer in-line with the air blower and the connecting air hose. Within the shell housing of the silencer is a sound-absorbing material that absorbs sound energy from the air flowing through the silencer.

Abstract: A device and method for counting particles on a sample surface. The device includes a scanner having a surface for interfacing with the sample surface. The scanner is connected to one end of a tube which has two canals. The other end of the tube is connected to the particle counter. One of the tube canals supplies air from the particle counter through holes in the scanner surface for dislodging and fluidizing particles on the sample surface. The other tube canal returns air with the sample surface particles to the particle counter. After the particles are counted they are removed from the air stream by a filter. The air is then recycled back through the supply canal of the tube to facilitate additional particle counting. The method for using the device involves passing the scanner over the sample surface for predetermined periods, and collecting, counting and computing the average relative number of particles per unit area.