Sierra Monitor Corporation Gas Sensor Datasheet

Selecting the location for placement of gas sensors involves several different factors. You must first
evaluate the gas risk in the facility. The risk assessment process is critical in both identifying the potential
consequences of a gas leak to personnel, facilities and the environment and establishing the liability to
the firm of a significant leak. Based upon the risk assessment you can decide what sensors are required.
Second, you must evaluate the physical location to determine the number of sensors required and their
placement.
Qualification:
The guidelines presented below are for
reference only. They are not exhaustive
and should not be substituted for a
professional analysis of the gas risk
problem.
address related subjects such as a
comprehensive hazard assessment, data
logging, system operation, system alarm
response and alarm procedures at the
facility.
A. Use engineering judgment
There are no complete and definitive
regulations or guidelines published by
ISA, NFPA, UL, FM or other agencies that
tell users where or how many gas sensors
1
to use. Each gas leak possibility must be
evaluated as a unique problem to assess
the risk to people and property.
object of monitoring s ystem design is to
reduce the risk to people and property by
responding to the gas leak.
Note 1: NFPA has published NFPA 73E
Standard on Automatic Fire Detectors,
Appendix A, which suggest that a diffusion
sensor used for smoke detection be
placed every 900 square feet of ceiling
space.
B. Consider
Probability
equipment
operating
composition of materials used, etc.)
Quantity of gas that could be present
Environmental conditions (i.e. wind
speed, wind direction, blowers/fans in
room, temperature, etc.
Sierra Monitor Corporation 1991 Tarob Court Milpitas, California 95035 (408) 262-6611 (800) 727-4377 fax: (408) 262-9042
These guidelines do not
of gas leaks
or material failure,
error, changes
Gas Sensor Placement Guidelines
Dilution rates and convection currents (as
affected by natural diffusion, forced air
ventilation procedure, etc.)
Density of gas (heavier or lighter than air
– see Chart 1)
Interfering gases
Chart 1: Gas Weight in Relation to Air for
Ammonia
Butane
Carbon Dioxide
The
Carbon Monoxide
Methane
Chlorine
Ethane
Ethylene
Heptane
Hydrogen
Hydrogen Chloride
Hydrogen Cyanide
Hydrogen Sulfide
Methyl Alcohol
(i.e.
Nitric Oxide
in
Nitrogen Dioxide
Pentane
Propane
Sulfur Dioxide
Toluene
Application Data Sheet
Typical Gases
Lighter
Heavier
Heavier
Slightly Lighter
Lighter
Heavier
Slightly Heavier
Slightly Lighter
Heavier
Lighter
Heavier
Lighter
Heavier
Heavier
Slightly Heavier
Heavier
Heavier
Heavier
Heavier
Heavier
ADS-001