Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Size Distribution and Light Scattering Properties of Test Smokes (NIST SP 965)



D W. Weinert, Thomas Cleary, George W. Mulholland


Measurements of particles size distributions and optical properties of smoke detector test smokes may yield a better understanding of existing detector designs and facilitate design improvements; NIST is making such measurements now on smokes produced in the fire emulator/detector evaluator (FE/DE). Results are presented for the first time of the mass scattering cross section (m2.g-1) of one flame generated (propylene) and two non-flaming fire generated tests smokes (cotton smolder, wood pyrolysis). Size characterization shows that the smoke from pyrolysed wood blocks is a unimodal distribution with a MMAD of 1.55 mm, while the smoldered cotton wick fuel has a bimodal distribution with a MMAD of 0.31 mm for its measurable mode. It was found that 48D% of the mass of the cotton wick smoke was below 0.056 mm. The ratio of polarization and the degree of linear polarization have been demonstrated as a means of distinguishing between soot from flaming fires and smoke particles from non-flaming fires. The ratio of polarization is shown to be more sensitive than the degree of polarization to soots from different flaming fuels. Three flame generated smokes (acetylene, ethylene and propylene) are shown to have similar q-plots, which are easily distinguished from the q- plots for the non-flaming fuels smokes.
Special Publication (NIST SP) - 965
Report Number


fire detection, fire detection systems, smoke detectors, smoke generation, size distribution, sampling, light scattering


Weinert, D. , Cleary, T. and Mulholland, G. (2001), Size Distribution and Light Scattering Properties of Test Smokes (NIST SP 965), Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed July 17, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created January 31, 2001, Updated October 12, 2021