A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
N.C.: Normally closed contacts of a relay. Contacts
are close-circuited when the relay is de-energized.
NEPHROTOXIN: A chemical which has a primary toxic
effect on the kidneys.
NEUROTOXIN: A chemical which has a primary toxic
effect on the central nervous system. Styrene,
mercury, carbon disulfide.
N.O.: Normally open contacts of a relay. Contacts
are open-circuited when relay is de-energized.
NATURAL VENTILATION: The movement of air into
and out of a space through intentionally provided
openings, such as windows and doors, or through
nonpowered ventilators or by infiltration.
NIOSH: The National Institute for Occupational
Safety and Health is a federal agency. It conducts
research on health and safety concerns, tests
and certifies respirators, and trains occupational
health and safety professionals.
NOISE CRITERIA CURVES (NC CURVES): Curves that
define the limits which the octave band spectrum
of a noise source must not exceed if a certain
level of occupant acceptance is to be achieved.
NOISE REDUCTION (NR): The difference between
the average sound pressure levels of two spaces.
Usually these two spaces are two adjacent rooms
called, respectively, the source room and the
receiving room.
NORMALLY OPEN (OR NORMALLY CLOSED): The position
of a valve, damper, relay contacts, or switch
when external power or pressure is not being applied
to the device. Valves and dampers usually are
returned to a "normal" position by a
spring.
NOSOCOMIAL INFECTIONS: The type of infections
that are acquired in hospitals.
NUISANCE DUST: Have a long history of little
adverse effect on the lungs and do not produce
significant organic disease or toxic effect when
exposures are kept under reasonable control.
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