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Model 850 Investigator’s Aid
Accelerant and Gas Detector
Operation and Maintenance
www.graceindustries.com
M850TM1215 © December 2015
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Model 850
Table of Contents
1. Cover
2. Table of Contents
3. Top View
4. Features & Benefits
5. Operation: Turning ON
6. Operation: Adjusting Sensitivity
7. Operation: Scanning for Gases
9. Operation: Electronic Purge
11. Operation: Battery Life
12. Operation: Charging the Battery
13. Maintenance: Battery Maintenance
14. Maintenance: Sensor Maintenance
15. Maintenance: Replacement of Sensor
18. Model 850 Warranty Information
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Plug-In Sensor
Removable
Guard Screen
Retractile Cord
Model 850
Top View
Sensor Guard
Telescoping Wand Locking Clips
Telescoping Wand
HI/LO Range Switch
Audio Annunciator
ON / OFF Switch and
Sensitivity Adjust Control
Analog Meter
Indicator LEDs
Battery Transfer Switch
Purge Indicator
Charge
Indicator
Battery
Charge
Jack
Mute Switch
Rubber Grip
Electronic
Purge
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Model 850
Features & Benefits
• Detects approx. 125 toxic/combustible gases and/or vapors including heating gases
• Adjustable Sensitivity aids in pinpointing the source of high gas concentration
• Solid State Sensor, housed in a protective guard, with a 6 foot coiled sensor cord
• Audio and Visual displays indicate the detection of suspect gases
• Powered by Nickel Cadmium rechargeable batteries with operating time of
approximately 8 hours of use
• Corrosion resistant, painted steel enclosure
• Electronic Purge permits quick recovery of sensor element
• Mute Switch turns off audio tones and permits discreet investigation
• Applications: Arson Investigation, Leak detection, General purpose gas detection
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Model 850 Operation
Turning ON
• Turn the Model 850 ON by rotating the ON/OFF &
Sensitivity Adjust Control clockwise until a click is heard.
• Allow approximately three (3) minutes for the sensor to
attain operating temperature and stabilize.
• A Mute switch is located on the side of the detector and
can be switched ON to silence the audio.
ON/OFF &
Sensitivity Adjust
Control
Mute
Switch
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Model 850 Operation
Adjusting Sensitivity
• Rotate the Sensitivity Adjust Control knob clockwise until
meter just starts to deflect.
• Place the Range switch in the “HI” position.
• Place the Purge and Mute switches in the down position.
• The Model 850 is now ready for use and has a sensitivity of
approximately 50 parts per million (ppm) for methane as the
test gas.
ON/OFF &
Sensitivity
Adjust
Control
Purge
Switch
Mute
Switch
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Model 850 Operation
Scanning for Gases
• Because the Model 850 is constantly sampling the
atmosphere and is dependent upon (hydrocarbon)
aerosol particles or gas molecules to diffuse into the
sensor, sufficient time should be allowed for this to
occur - usually 4 to 5 seconds.
• When attempting to locate very small leaks or
hydrocarbon vapors, slowly scan the area in question,
holding the Model 850 at a 45 degree angle and one
inch from the area being examined.
• When gas or accelerants are detected, the audio and
visual indicators will beep and flash in synchronism.
Beep and flash rates will increase when higher
concentrations of gas/hydrocarbons are discovered.
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Model 850 Operation
Scanning for Gases
• Consideration must be given to factors such as time,
temperature and relative humidity.
• Most accelerants/hydrocarbons are more pronounced
as aerosol particles on warm, dry days than on cold,
damp days. These factors will influence the volatility of
hydrocarbons.
• If there is an area of suspicion and you do not get a
reading, put the Model 850 in its most sensitive mode
(indicated by a very slow beep and flash rate) and
observe if any change in beep rate occurs upon further
investigation of the suspect area.
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Model 850 Operation
Electronic Purge
• The Electronic Purge feature permits a rapid recovery of
the sensor element.
• After the Model 850 has detected the presence of an
accelerant, simply slide the Purge Switch to the ON
position; the Yellow Purge Indicator Light will glow Red.
• Leave the Purge Switch in the ON position for 15 to 30
seconds. There may be rapid beeping as the sensor burns
off residual vapors.
Purge
Switch
• After 15 to 30 seconds, slide Purge Switch to OFF position.
• The unit will rapidly cease to annunciate and the Model 850
is now ready to detect another sample.
• Before attempting to detect another sample: Turn Purge
Switch OFF and reset sensitivity.
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Model 850 Operation
Electronic Purge
• The Purge Switch may also be used to speed the warm-up
period when the unit is initially turned on.
• When the Purge Switch is in the ON position, the detector’s
circuits are disabled and the Model 850 will NOT detect the
presence of gas or accelerants in this mode.
• Turn Purge Switch OFF before attempting to detect a
suspect area.
Purge
Switch
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Battery
Transfer
Switch
Model 850 Operation
Battery Life
• Model 850 is powered by two nickel cadmium cells.
• Operating time for each cell is 4 hours.
Total operating time is approximately 8 hours.
• When battery power is low, a slow beeping sound will be
observed. Note: the low-battery indication is audio only.
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Model 850 Operation
Charging the Battery
To charge your Model 850:
• Turn unit OFF and insert charger plug into the Battery
Charging Jack on the side of the unit.
• Plug the charger/adapter into power source/outlet.
Battery Charging Indicator Light will glow Red while the
unit is charging.
• NOTE: Both battery banks charge simultaneously.
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Model 850 Maintenance
Battery Maintenance
• For optimum performance from your Model 850, the
following procedures are recommended:
• Be certain the Model 850 is used a minimum of ten (10)
hours per month, preferable several hours each week. If the
unit is used less than ten hours, the following procedure
should be observed to maintain peak performance.
• Turn the unit ON and let the batteries completely discharge.
• When battery power is low, a slow beeping sound will be
observed. Let the batteries fully discharge before turning the
unit OFF and recharging the batteries.
NOTE: the low-battery indication is audio only.
• This procedure conditions the battery for maximum power
and also re-sensitizes the sensor by removing any absorbed
gases that may have absorbed into the sensor.
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Model 850 Maintenance
Sensor Maintenance
• Avoid getting debris or foreign material in the sensor.
• If the sensor becomes contaminated, let the unit warm up
and then lightly tap the sensor over a white piece of paper
and observe if any material is dislodged.
• The white paper will readily show any foreign debris that
may have been lodged in the sensor.
• If the sensor should accidentally become submerged in
liquid, let the sensor dry out for 24 hours. Turn unit ON for 8
hours until the batteries are exhausted.
• Charge the batteries and repeat above procedure.
• Spare sensors are available from the factory if replacement
becomes necessary.
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Model 850 Maintenance
Replacement of Sensor
• Remove sensor guard screen.
• Remove damaged or malfunctioning sensor from the socket located at the end of the
telescoping probe.
• Use a small screwdriver to carefully and incrementally loosen the sensor from the
socket.
• Once it is loose, pull the sensor out of the sensor housing.
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Model 850 Maintenance
Replacement of Sensor
• Plug in new replacement sensor by carefully aligning the sensor pins into the socket.
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Model 850 Maintenance
Replacement of Sensor
• Gently and firmly press the replacement sensor into the socket until it is secure.
• Allow for required warm-up period (approximately three (3) minutes) before use.
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Model 850
Warranty Information
Grace Industries, Inc. warrants Grace Industries, Inc. portable
hydrocarbon detector Model 850 to be free from defects in
workmanship and materials for a period of one year from the
date of purchase. Grace Industries, Inc. will not repair or replace
any merchandise under warranty which has been damaged
because of accident, misuse or abuse while in possession or
control of the consumer. This warranty is void if any attempt to
repair or replace parts was made or attempted by other than
qualified Grace Industries, Inc. personnel. This warranty is void
if any of the sealed compartments are opened or tampered with.
Send all returned merchandise, prepaid to: Grace Industries,
Inc., Repair Division, 305 Bend Hill Road, Fredonia, PA 16124
USA. Grace Industries, Inc. shall not be liable for any direct,
incidental or other consequential loss or damage arising out of
the failure of the product to operate.
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Model 850 Investigator’s Aid
www.graceindustries.com
M850TM1215 © December 2015
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