P
Particle (Contamination Control) A
minute quantity of solid or liquid matter.
Particle Counter, Airborne An instrument
for continuous counting of airborne particles larger than a given
threshold size. The sensing means may be optical, electrical,
aerodynamic, etc.
Particle Counter, Optical A light
scattering instrument with display and/or recording means to count and
size discrete particles in air, as defined by ASTM F-50-83.
Particle Size The maximum linear dimension
of a particle as observed with an optical microscope or the equivalent
diameter of a particle detected by an instrument. The equivalent
diameter is the diameter of a reference sphere having known properties and
producing the same response in the sensing instrument as the particle
being measured.
Particulate A substance which consists of
particles. (ex. flour, rouge, clay).
Particulate Contaminant A contaminant
consisting of particles.
Particulates, Airborne See Airborne
Particles
Permeability The process whereby a fluid or
gas passes through a barrier at the molecular level. Passage of
these materials through defects such as holes or tears does not constitute
permeability.
Precision The degree of agreement of
repeated measurements of the same property, expressed in terms of
dispersion of test results about the mean result obtained by repetitive
testing of a homogenous sample under specified conditions. The
precision of a method is expressed quantitatively as the standard
deviation computed from the results of a series of controlled
determinations.
Pressure, Static The pressure of a fluid at
rest, or in motion, exerted perpendicularly to the direction of flow.