AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Characterization of Ventilation and Ultrafine Particles Clearance in a Closed Firing Range during Firing of Lead Free Frangible Ammunition
CHRISTIN GRABINSKI, Trevor Tilly, Claude Grigsby, Saber Hussain, Darrin Ott, Air Force Research Laboratory
Abstract Number: 718 Working Group: Aerosol Exposure
Abstract Range instructors have reported respiratory symptoms during firing of lead free frangible (LFF) ammunition. However, exposure assessments have detected chemicals and particulate matter (PM) in amounts much lower than their respective exposure limits. We hypothesize that ultrafine PM comprise a large fraction of firing emissions, which does not contribute to mass concentration, but may be related to respiratory symptoms due to high particle number concentration. We further plan to characterize the ventilation in the closed environment using ultrafine PM as a dynamic real-time metric. We measured PM emissions in the breathing area of instructors at an indoor small arms firing range using LFF ammunition. Real-time measurement of particle number concentration and size distribution was completed using direct reading instruments. PM was collected onto substrates for morphology and elemental analysis using electron microscopy and energy dispersive X-ray spectroscopy. PM was also collected onto mixed cellulose ester membranes, which were weighed for mass measurements, then digested and analyzed for key metals using inductively-coupled plasma mass spectrometry. The real-time measurements indicated the emission of ultrafine PM during firing and indicated a dynamic response to variations in the ventilation system. The PM coalesced and cleared the range at different rates depending on the weapon. Distinct morphologies in the ultrafine size range were observed, and the composition was found to include many elements, such as carbon, copper, zinc, bismuth and sulfur. The mass of key metals was several orders of magnitude below mass-based exposure limits. Number-based exposure limits may be more relevant for exposures where ultrafine PM is emitted. Further, ventilation design and particle filtering techniques in small arms firing ranges should be optimized for clearance of firing emissions. Therefore, a personal monitoring size direct read ultrafine particle instrument is recommended for future assessment of ventilation health and firing emission clearance in closed firing ranges.