MiniCapt® Mobile Operations Manual
D-1
Appendix D
Compressed Gas Sampling Operation
Introduction
The MiniCapt
®
Compressed Gas Kit allows the MiniCapt Mobile Microbial Air Sampler
to perform microbiological monitoring of compressed gases. This kit uses a special
diffusion chamber mounted directly to the MiniCapt inlet, the other end of which is
connected directly to the high pressure gas distribution lines.
The sampling is performed at balanced flow, where the compressed gas flow is equal
to the sampling flow. The BioCapt
®
Impactor inlet pressure coincides with the pressure
of the kit’s diffusion chamber.
For safety reasons and to regulate the flowrate of the gas into the diffusion chamber, a
pressure regulator is installed in the sampling line between the high pressure gas
source and the inlet to the MiniCapt Mobile Compressed Gas Kit. A solenoid valve is
connected downstream of the regulator and allows the MiniCapt to synchronize the
flow of the gas with the start of sampling.
The Compressed Gas Kit is designed to work with either the 25 LPM, 50 LPM, or 100 LPM
MiniCapt systems. The flow of the gas to be sampled is controlled using the principle
of the critical orifice. Under operating pressures, the critical orifice regulates the
flowrate into the diffusion chamber and the exhaust. The pressurized gas flowrate
must be within ±5% of the airflow rate through the MiniCapt Mobile. To aid in ensuring
the pressure in the diffusion chamber and the flowrate through the MiniCapt are within
the correct ranges, the MiniCapt system actively monitors the gas flow should there be
a change in flow.
