These methods cover the measurement of atmospheric pressure with
two types of barometers: the Fortin-type mercurial barometer and
the aneroid barometer.
In the absence of abnormal perturbations, atmospheric pressure
measured by these methods at a point is valid everywhere within a
horizontal distance of 100 m and a vertical distance of 0.5 m of
Atmospheric pressure decreases with increasing height and varies
with horizontal distance by 1 Pa/100 m or less except in the event
of catastrophic phenomena (for example, tornadoes). Therefore,
extension of a known barometric pressure to another site beyond the
spatial limits stated in 1.2 can be accomplished by correction for
height difference if the following criteria are met:
The new site is within 2000 m laterally and 500 m
The change of pressure during the previous 10 min has been less
than 20 Pa.
The pressure, P2 at Site 2 is a function of the known
pressure P1 at Site 1, the algebraic difference in height
above sea level, h1 − h 2, and the average
absolute temperature in the space between. The functional
relationship between P1 and P2 is shown in 10.2.
The difference between P1 and P2 for each 1 m of
difference between h1 and h2 is given in Table 1
and 10.4 for selected values of P1 and average
Atmospheric pressure varies with time. These methods provide
instantaneous values only.
The values stated in SI units are to be regarded as the
This standard does not purport to address all of the safety
concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and
health practices and determine the applicability of regulatory
limitations prior to use. Specific safety precautionary
statements are given in Section 7.
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