January 2002

BFRL Monthly Highlights

January 2002

February 2002

March 2002

April 2002

May 2002

PAST Highlights

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Verification of Calibration Procedure for Testing Military Gas Masks

Military personnel wear gas masks for protection against a chemical and biological assault. The recognized potential global threat from chemical and biological agents demands that effective defense measures be taken. An important part of this defense strategy is the testing and verification that assures secure gas mask fits. The Army determines the gas mask fit quality by measurement and comparison of the ambient aerosol concentration outside of the fitted masks to the aerosol concentration inside that results from penetration of the mask. The concentration measurements are made using a portable condensation particulate counter (CPC), the M41.

Currently, are no aerosol concentration standards for the CPCs, nor are there certified reference materials available for aerosol concentration standardization. The measurement process currently has no links or traceability to a standards granting organization. The U.S. Army Test, Measurement, and Diagnostic Equipment Activity requires the development of an aerosol concentration standard method, traceable to NIST.

CSTL and BFRL staff are working with the U.S. Army Test, Measurement, and Diagnostic Group to verify the accuracy of the CPC calibrant that is used to test and verify the M41 CPCs by comparison measurements by a primary particle counting approach using electron microscopy and a secondary approach of determining the particle concentration in terms of electrical current using an aerosol electrometer. NIST has acquired test equipment and assembled an aerosol test stand that will deliver 80 nm diameter aerosol for measurement by a CPC, an aerosol electrometer and by electron microscopy. Calculations have been completed that simulate particle loss in the CPC. A method has been developed to provide NIST traceable calibration of the aerosol electrometer and some preliminary scanning electron microscopy has been undertaken to understand the problems associated with count metrology of 80 nm particles.

This verification of the calibrant CPC and possible development of a standard method will enable the accurate calibration of CPCs that are currently used for the calibration of military gas masks.

CONTACT: Robert Fletcher, 301-975-3912
Surface and Microanalysis Science Division
Chemical Science and Technology Laboratory (CSTL)

Public Release of the NIST Fire Dynamics Simulator 2.0

Official release versions of NIST’s computer programs for modeling and visualizing fire and smoke flow, Fire Dynamics Simulator 2.0 and Smokeview 2.0, are now available for download at http://fire.nist.gov/fds/. The NIST Fire Dynamics Simulator predicts smoke and/or air flow movement caused by fire, wind, ventilation systems, etc. Smokeview visualizes the predictions generated by the Fire Dyanamics Simulator.

The Fire Dynamics Simulator is a computational fluid dynamics model which solves a form of the Navier-Stokes equations appropriate for low-speed, thermally-driven flows of smoke and hot gases generated in a fire. Version 2.0 of the Fire Dynamics Simulator includes improved combustion and radiation algorithms. Details of the numerical methods may be found in the Fire Dynamics Simulator Technical Reference Guide
(NISTIR 6783). Smokeview visualizes the Fire Dynamics Simulator computed data by animating time dependent particle flow, two-dimensional slice contours and surface boundary contours. Details about Smokeview may be found in the Smokeview User’s Guide (NISTIR 6761). Version 2.0 of Smokeview includes new visualization techniques such as animated isosurfaces and animated flow vectors. Instructions on how to use the Fire Dynamics Simulator and Smokeview can be found in the Fire Dynamics Simulator User’s Guide (NISTIR 6784).

CONTACT: 
Glenn Forney (Smokeview), 301-975-2313 
Kevin McGrattan (FDS), 301-9752712
Fire Research Division

 

 

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