Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Aug-Sep;37(7-8):405-414.
doi: 10.1080/08958378.2025.2565730. Epub 2025 Sep 29.

A positive pressure system for selective human exposure to gas and particulate mixed atmospheres

Jacob S Griffin  1 , S Thorne Gregory  2 , Thomas E Austin  2 , Ingrid George  3 , Joseph Martin  3 , Lauren Slaber  3 , Jon Berntsen  2 , Steven E Prince  4 , James M Samet  5
Affiliations

A positive pressure system for selective human exposure to gas and particulate mixed atmospheres

Jacob S Griffin et al. Inhal Toxicol. 2025 Aug-Sep.

Abstract

Introduction: Exposure to air pollution containing particulates (PM) and gas-phase volatile organic compounds (VOCs), is a leading cause of human morbidity and mortality globally. Devising effective protective public health strategies requires an assessment of the relative contribution of PM and VOCs to the health effects of air pollution exposure.

Methods: To enable studies of VOCs isolated from mixed atmospheres, we developed a positive air pressure exposure system that permits the subject to breathe unimpeded by the pressure drop imposed by filtering respirators. This system uses pumps to draw air through respirator filters and delivers it to a modified positive pressure respirator at a flow rate that exceeds the ventilatory requirements of the wearer, while preventing infiltration of the surrounding atmosphere.

Results: Tests showed negligible leaks (<5% flow reduction) and minimal VOC losses (95% recovery) to the system. When tested using an atmosphere containing woodsmoke, PM filters showed effective exclusion of particulates but minimal losses of VOCs, while activated carbon based cartridges effectively removed gaseous compounds and PM. A team member exercising moderately in a woodsmoke atmosphere for 2-hours reported no perveivable odors and experienced no discomfort during an exposure using charcoal filter cartridges.

Discussion: We report the development and validation of a novel human exposure system that allows selective exposure to the gaseous fraction of a mixed atmosphere. This system allows for moderate to vigorous exercise of the study subject and can be used in place of an exposure chamber, making it compatible with clinical and field studies.

Keywords: Clinical exposure system; air pollution; human studies; respiratory protection.

Plain language summary

Developing strategies to protect the public from exposure to air pollution requires studying the relative toxicity of gaseous and particle mixtures.Studies can be conducted in human volunteers wearing tight-fitting respirators that filter out gases and/or particles.However, respirators require considerable effort to breathe against, and this negative pressure limits the exertion that the wearer can perform.We therefore developed and tested an exposure system that uses external pumps to deliver filtered air under positive pressure to the breathing zone of a volunteer undergoing moderate exercise.We show that the system can be used to effectively filter particles, allowing gaseous compounds in the exposure atmosphere to pass through, while the study volunteer exercises comfortably at moderately strenuous levels.This novel exposure system is compatible with standard respirator filters and can be used for clinical and field studies.

PubMed Disclaimer

LinkOut - more resources