Abstract: An apparatus for the continuous collection of a time-weighted gas sample is disclosed. The apparatus inclues a gas reservoir and an openable and closeable gas flow assembly communicating with the reservoir which assembly allows gas to flow at a constant rate from the exterior of the reservoir to the interior of the reservoir when there is a sufficient gas pressure differential between the exterior and interior of the reservoir so that the passing gas achieves a linear velocity in the throat of the gas flow assembly equal to the velocity of sound in the passing gas in the throat. The apparatus of this invention may also include additional gas sample removal assemblies attached to the reservoir.