Abstract: Relatively accurate gravimetric analysis of airborne particulate matter in a sample is achieved by making gravimetric measurements of the sample on a microbalance in a closed chamber, continuously electronically monitoring air pressure, humidity and temperature in the chamber, continuously controlling humidity and temperature in the chamber, and combining the gravimetric measurement with measurements of air pressure, humidity and temperature in the chamber to make a buoyancy corrected determination of the mass of the particulate matter.

Abstract: Relatively accurate gravimetric analysis of airborne particulate matter in a sample is achieved by making gravimetric measurements of the sample on a microbalance in a closed chamber, continuously electronically monitoring air pressure, humidity and temperature in the chamber, continuously controlling humidity and temperature in the chamber, and combining the gravimetric measurement with measurements of air pressure, humidity and temperature in the chamber to make a buoyancy corrected determination of the mass of the particulate matter.

Abstract: An apparatus for exposing laboratory animals to test substances comprises, generally, at least two supply manifolds for supplying each a gaseous or a vaporous substance, an exhaust manifold for removing an exhalate of said animals and unused portion of said test substance, and a plurality of inhalation chambers. Each chamber is dimensioned to accommodate a nasal part of the animal's head and is in fluid communication with the at least two supply manifolds and with the exhaust manifold. The apparatus is designed to prevent the streams of test substances hitting the animal's nostrils and causing an avoidance reaction.