Design, construction and operation of a simple inhalation exposure system

Abstract

An inhalation exposure system was designed from an all glass aquarium with a volume of 391 liters. A top for the chamber was fabricated from acrylic plastic and Teflon ê (surface in contact with the test atmosphere) with an inlet, outlet, 5 sampling ports, and handles. Supply air to the chamber was charcoal and HEPA filtered. Air flow through the chamber is horizontal and can range from 50 to 200 liters/minute. Air flow is measured by a glass tube rotameter and regulated by polyvinyl chloride valves. Chamber air was HEPA and charcoal filtered prior to exhausting it to ambient air. The operating characteristics of this exposure system were assessed using test atmospheres of formaldehyde, chlorine, n-hexane and an aerosol of propylene glycol. Expressed as percent of a central sampling point the chamber concentrations of formaldehyde, chlorine and n-hexane ranged from 91.6% to 103.3% with an average of 97.9%. No differences in chamber distribution were noted at 78 or 130 liters/minute (corresponding to 12 and 20 chamber volumes/hour). For propylene glycol, the mass median aerodynamic diameter (MMAD) at a chamber air flow of 79 L/minute varied from 1.37 to 1.63 μm (σg range 1.34 to 1.43). Similar results were found at 130 liters/minute. During mass sampling a concentration gradient was found from the inlet to the outlet of the chamber and ranged from 55 to 99% (¯x = 78.5%) of the inlet concentration. This inhalation exposure system is very suitable for acute or sub-acute inhalation studies of gases or vapors but is only satisfactory for aerosols under certain operating conditions. It should prove to be particularly useful for laboratories wishing to set up a modest inhalation toxicology facility.