This CDC developed physiologic sampling pump (PSP) overcomes shortcomings of previous devices by the use of calibrated valves in conjunction with a constant speed pump. This novel approach obviates typical PSP inertia that inherently limits system response, functionality and accuracy. All prior PSP designs have attempted to follow a user's breathing pattern by changing pump speed, thereby altering sampling rate. In that approach, pump inertia will limit system response and function due to the time required to adjust speed. Additionally, variable pump speeds often produce size selective sampling errors at low flow rates.

Performance of this PSP is not degraded by pump inertia or low flow size selective sampling errors. This design maintains a consistent pump speed, controlling PSP sampling rate with calibrated valves that redirect air flow almost instantaneously. In situ device testing demonstrated that when this air-flow valve is properly integrated into a sampling head, response time of the PSP is essentially mutually exclusive of the magnitude of changes in the effective flow, facilitating consistently small error in sampling performance regardless of user-exertion scenario.