Proceedings Article | 8 September 2010
KEYWORDS: Particles, Contamination, Fluctuations and noise, Buildings, Failure analysis, Carbon, Gases, Atmospheric particles, Environmental monitoring, Semiconducting wafers
Brush and forest fires, both naturally occurring and anthropogenic in origin, in proximity to space flight hardware
processing facilities raise concerns about the threat of contamination resulting from airborne particulate and molecular
components of smoke. Perceptions of the severity of the threat are possibly heightened by the high sensitivity of the
human sense of smell to some components present in the smoke of burning vegetation.
On August 26th, 2009, a brushfire broke out north of Pasadena, California, two miles from the Jet Propulsion
Laboratory. The Station Fire destroyed over 160,000 acres, coming within a few hundred yards of JPL. Smoke
concentrations on Lab were very heavy over several days. All Lab operations were halted, and measures were taken to
protect personnel, critical hardware, and facilities. Evaluation of real-time cleanroom monitoring data, visual inspection
of facilities, filter systems, and analysis of surface cleanliness samples revealed facility environments and hardware were
minimally effected.
Outside air quality easily exceeded Class Ten Million. Prefilters captured most large ash and soot; multi-stage filtration
greatly minimized the impact on the HEPA/ULPA filters. Air quality in HEPA filtered spacecraft assembly cleanrooms
remained within Class 10,000 specification throughout. Surface cleanliness was minimally affected, as large particles
were effectively removed from the airstream, and sub-micron particles have extremely long settling rates. Approximate
particulate fallout within facilities was 0.00011% area coverage/day compared to 0.00038% area coverage/day during
normal operations. Deposition of condensable airborne components, as measured in real time, peaked at approximately
1.0 ng/cm2/day compared to 0.05 ng/cm2/day nominal.
