A particulate sample collector has a blower to draw air through ducting in which a filter collects particles. The blower is driven by a sealed inductive A.C. motor. A throttle in the ducting is controlled by a pneumatic motor in response to variation in pressure drop, to provide constant mass flow rate as the filter gradually becomes clogged.

An improved dosimeter having a low air flow rate for monitoring working areas in which air is pumped through the dosimeter at a controlled constant low rate of flow and any particles or vapors in the air are collected on a filter, a variable drive pump having an inlet and an outlet is connected to the filter and is driven by an electric motor and controlled by a feed back circuit of an integrator and an amplifier and the pump maintains a constant flow of air through the dosimeter; in operation of the dosimeter the integrator receives a signal from a pressure switch that detects changes in the flow of the air stream through the dosimeter by a change in a pressure drop of the air which is being pumped through an orifice; The improvement is the use of an adjustable by-pass valve connected in parallel with the variable drive pump in such a manner that regulated quantities of air from the outlet of the pump are recycled to the inlet of the pump thereby allowing the pump to provide a constant low flow rate of air; In utilization of the dosimeter, the dosimeter is placed in a work area or worn by an individual and at the termination of a period of time, such as a work day, the filter is removed and the contents collected are analyzed by conventional techniques such as gas chromatography to determine a level of exposure of individuals working in that area.

An air sampling device comprises a pump assembly including a pump and a motor operably associated with the pump, the air flow rate of the assembly being substantially characterized by a function having a plurality of measurable variables; sensors for periodically automatically monitoring the variables; a programmable computer operably associated with the sensors for periodically estimating the instantaneous air flow rate of the pump from the function and the monitored variables and for camparing the calculated instantaneous air flow rate with a previously programmed desired air flow rate; and a DC-DC converter responsive to the computer and operably associated with the motor for modulating the motor speed in response to the computer to thereby cause the instantaneous air flow rate of the pump to approach the desired air flow rate.

A microprocessor controlled air sampling pump utilizes a PWM controlled DC electric motor for regulating air flow generated by a diaphragm-type air pump. The control system regulates air flow as a function of RPM of the motor by establishing a table of values which relate motor RPM to air flow rates. The control system maintains RPM at the desired value but includes a control loop which senses deviations in RPM and adjusts the PWM signals to the motor to regulate RPM. The system also senses large changes in RPM and treats such changes as blockages in the air sampling pump lines which prevent accurate environmental sampling. This system enters a cycling mode which turns the pump motor off for different time intervals until the detected blockage has been removed or until a predetermined time has expired. This procedure minimizes battery drain in the event of blockage of the air sampling pump lines. It also provides a method of accurately monitoring pump run time since it shuts off the pump during times in which the air flow is blocked.

An air-sampling cartridge is disclosed for collecting organic compounds such as N-nitrosamines from air for analysis. The cartridge is formed by joining two injection-molded plastic parts: a generally cylindrical cartridge body into which air-pervious packings of granular adsorbent materials may be loaded, and a cartridge cap which is ultrasonically welded to the body to partially close one end of the cartridge. The cap and body define a cartridge with an inlet and outlet shaped to facilitate connection of the cartridge to a pump used to draw air samples through the cartridge, to allow connection of two or more cartridges in series, and to accommodate standard-sized syringes used in removing trapped compounds from the cartridge for analysis. The cartridge also includes a retention clip integrally molded with the cartridge body and cap for permitting the cartridge to be attached to the clothing of a person during air-sampling. Also provided are two shipping caps which are held within storage wells on the cartridge body during air-sampling and which at other times are used to seal the inlet and outlet of the cartridge to prevent contamination of the adsorbent material and compounds trapped therein.