Instruction manual

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In the following table "NA" indicates no value has been
assigned by OSHA.
Note: Customers should be aware that OSHA
permissible exposure limits may be subject to
change.
Recent court decisions have affected the
enforcement of permissible exposure limits
published or modified since the initial enactment of
OSHA in 1971. The following table shows the OSHA
permissible exposure limits as published in the 1989
edition of the Code of Federal Regulations (29 CFR
1910.1000). It is recommended that customers verify
that the values given below are correct and current
before using them to update their alarm set-points.
OSHA (1989) Permissible Exposure Limits:
Gas Ceiling STEL TWA
CO 200 ppm NA 35 ppm
H2S NA 15 ppm 10 ppm
SO2 NA 5.0 ppm 2.0 ppm
5. PhD Ultra default alarm settings
The most conservative possible way to set alarms is the
method used by Biosystems for the PhD Ultra 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.
Gas Ceiling TWA STEL
CO 35 ppm 35 ppm 100 ppm
H
2
S 10 ppm 10 ppm 15 ppm
SO
2
2.0 ppm 2.0 ppm 5.0 ppm
Cl
2
0.5 ppm 0.5 ppm 1.0 ppm
HCN 4.7 ppm 4.7 ppm 4.7 ppm
NH
3
25 ppm 25 ppm 35 ppm
NO 25 ppm 25 ppm 25 ppm
NO
2
1.0 ppm 1.0 ppm 1.0 ppm
Oxygen (O
2
) Low alarm:
19.5%
High alarm:
22.0%
Combustible gas 10 % LEL
Biosystems PhD Ultra default alarm settings
Note: When a “CO Plus” sensor is installed the
default alarm settings are automatically assigned on
the basis of the calibration gas selected for use. If
carbon monoxide is selected as the calibration gas,
carbon monoxide alarm settings are automatically
assigned. If hydrogen sulfide is selected as the
calibration gas, hydrogen sulfide alarm settings are
automatically assigned.
Appendix C How to calibrate your PhD
Ultra in contaminated air
Calibration of the PhD Ultra 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 owners manual.