GasTech D-Guard2, Руководство оператора

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D-Guard
2
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9.5.2 Detector Location
Although over time, gas released into a space will expand to uniformly fill it with equal concentration, in many
practical applications, there exists the possibility of pooling due to areas that have little or no ventilation or
natural movement of air. For these locations higher than average concentrations of any gases present may exist
since natural diffusion could well be a slower process compared to the rate at which gas is entering the area. In
working environments where there is a likelihood of these situations occurring, proper consideration to the
location of gas detection instruments is important.
The specifics as to what constitutes the ideal location for gas detectors are strongly dictated by the actual
physical makeup of the environment. Considerations could be for example: - likely points of release, location of
personnel in relation to points of release, ventilation characteristics, temperature, volume of space in and
around personnel (open or confined space) and maximum time durations for exposure to any released gases.
Knowing the characteristics of the gases to be monitored can assist in deciding on optimal locations. Permissible
exposure levels are covered by various health and safety standards and are not reproduced in this manual.
A characteristic of significant interest is the buoyancy of the gas in air, essentially whether it is more or less
dense than air. Knowing this can provide some indication of areas of possible pooling or areas near a point of
release that leaked gas will initially move towards.
Table 2: Absolute and Relative Densities of Common Gases Referenced Against Air.
* Absolute densities are given at STP 101.3kPa / 15⁰C unless otherwise noted
Gas Density (kg/m
3
) @ STP 101.3kPA/15⁰C Relative Density (Air = 1.0) Heavier or Lighter Than Air
Air 1.225 1.0 -
Ammonia 0.7289 0.595 Lighter
Carbon Monoxide 1.1849 0.967 Lighter
Chlorine 3.04 2.480 Heavier
Ethylene Oxide 1.8375 (101.3kPa / 20⁰C) 1.52 Heavier
Fluorine 1.6074 1.312 Heavier
Hydrogen 0.0852 0.0695 Lighter
Hydrogen Chloride 1.56 1.274 Heavier
Hydrogen Cyanide 1.15 0.94 Lighter
Hydrogen Sulphide 1.4534 1.186 Heavier
Nitrogen Dioxide 3.21 2.62 Heavier
Nitric Oxide 1.3402 (101.3kPa / 0⁰C) 1.094 Heavier
Ozone 2.154 (101.3kPa / 0⁰C) 1.758 Heavier
Phosphine 1.45 1.184 Heavier
Sulphur Dioxide 2.7633 2.256 Heavier
Oxygen 1.354 1.105 Heavier
Methane 0.6797 0.555 Lighter
Carbon Dioxide 1.8714 1.53 Heavier