Carbon Monoxide Alarm User Manual

Page 41
5. PhD
2
default alarm settings
The most conservative possible way to set alarms is the
method used by Biosystems for the PhD
2
default alarm
settings. The Ceiling alarm is set at the factory at the 8
hour TWA level (when this is given). With this setting, it
is unlikely that either the STEL or TWA alarm will ever be
activated. For other values, contact Biosystems or your
authorized distributor.
Biosystems PhD
2
default alarm settings:
Gas Ceiling TWA STEL
CO 35 PPM 35 PPM 100 PPM
H2S 10 PPM 10 PPM 15 PPM
SO2 2.0 PPM 2.0 PPM 5.0 PPM
Cl2 0.5 PPM 0.5 PPM 1.0 PPM
HCN 4.7 PPM 4.7 PPM 4.7 PPM
NH3 25 PPM 25 PPM 35 PPM
NO 25 PPM 25 PPM 25 PPM
HCl 5.0 PPM 5.0 PPM 5.0 PPM
NO2 1.0 PPM 1.0 PPM 1.0 PPM
Oxygen (O
2
) Low alarm:
19.5 %
High alarm:
23.5 %
Combustible gas 10 % LEL
Appendix C How to calibrate your PhD
2
in contaminated air
Calibration of the
PhD
2
is a two-step process. The first
step is to expose the sensors to contaminate-free air with
an oxygen concentration of 20.9% and perform a fresh air
calibration.
Unfortunately, there are some locations which are never
completely free of contaminants. An example would be a
furnace intensive area which always has a background
concentration of a few PPM CO. To make calibration
easy in this case, it is necessary to use special calibration
"Zero Contaminant" gas. This gas cylinder, Biosystems
part number 9039, is used in conjunction with the sample
draw calibration adapter. Flow the zero contaminant gas
across the sensors for a minute, just as if you were doing
a span calibration. Then do the fresh air calibration steps
described in Chapter 3 of the owner’s manual.