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Gas detector / sensor (CO and NO2) · BACnet points list
Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP) BACnet points list
Updated 6 November 2026
The GDT is a Greystone CO and NO2 gas detector with native BACnet MS/TP. Gas and temperature readings are Analog Inputs; buzzer, strobe and two relay alarms (setpoint, hysteresis, delay) plus sensor-life and recalibration timers are Analog Values; Binary Values enable, test and reset each function, and twelve Binary Inputs report sensor presence, alarms and service states.
This page lists 63 BACnet objects for the Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP) — 48 of them writable — with each object’s type, instance number, name, engineering units and access. It is re-typed from Greystone Energy Systems’s own free documentation, linked below.
- Manufacturer
- Greystone Energy Systems
- Model
- GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP)
- Equipment
- Gas detector / sensor (CO and NO2)
- Equipment type
- Thermostats, sensors & meters
- BACnet objects
- 63 (48 writable)
- Transport
- BACnet MS/TP
- Firmware
- 1.0 (PICS, July 10, 2019)
- Default device instance
- 381003
- Also known as
- GDT, GDTXXXBAC, GS, Greystone CO NO2 gas detector, parking garage gas detector
Reference only, provided as-is: verify against Greystone Energy Systems’s current documentation and the live device before use. Not official Greystone Energy Systems information. Terms of use.
BMS integration notes: Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP)
Set the MS/TP MAC in the menu, then read CO and NO2 and the alarm, fault and recal BIs. Assign and set the two relay alarms once; they usually start garage exhaust fans locally.
Minimum points to map
The short list most integrators start with — enough to run the unit from a BMS. Map more as the job needs.
| Object | Name | Why | Access |
|---|---|---|---|
| AI 1 | CO Sensor Value | CO level, ppm | Read |
| AI 2 | NO2 Sensor Value | NO2 level, ppm | Read |
| BI 5 | Alarm1 Status | Alarm / relay 1 active (fan stage 1) | Read |
| BI 6 | Alarm2 Status | Alarm / relay 2 active (fan stage 2) | Read |
| BI 3 | Device Status | General device alarm | Read |
| BI 8 | CO Fault Mode Status | CO sensor end-of-life fault | Read |
| BI 9 | NO2 Fault Mode Status | NO2 sensor end-of-life fault | Read |
Network setup
- Device instance defaults to 381003 (381000 + MAC); it stops following the MAC once written over BACnet.
- MS/TP baud rates 9600-115200 are supported.
Watch out for
- With BV 7 = Manual Reset, alarms latch until reset.
- After replacing or recalibrating a sensor, reset its fault and recal timers (BV 14/16/18/20).
Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP) BACnet objects
Type: AI, AO, AV, BI, BO, BV, MI/MO/MV (multi-state) · Access: Read read-only, Write writable, Command writable with a priority array.
| Description | States | |||||
|---|---|---|---|---|---|---|
| AImin | 1 | CO Sensor Value | CO, 0-500 ppm | ppm | Read | |
| AImin | 2 | NO2 Sensor Value | NO2, 0-10 ppm | ppm | Read | |
| AI | 3 | Temperature Sensor Value | Temperature, -20 to 50 °C | °C / °F | Read | |
| AV | 1 | CO Buzzer Setpoint | CO buzzer level, 20-500 ppm (default 150) | ppm | Write | |
| AV | 2 | CO Buzzer Delay | CO buzzer delay, 0-10 min (default 5) | min | Write | |
| AV | 3 | NO2 Buzzer Setpoint | NO2 buzzer level, 1-10 ppm (default 2) | ppm | Write | |
| AV | 4 | NO2 Buzzer Delay | NO2 buzzer delay, 0-10 min (default 5) | min | Write | |
| AV | 5 | Alarm1 Setpoint | Alarm/relay 1 level (default 50 ppm CO or 2 ppm NO2) | ppm | Write | |
| AV | 6 | Alarm1 Hysteresis | Alarm 1 hysteresis (default 10 ppm CO or 0.5 ppm NO2) | ppm | Write | |
| AV | 7 | Alarm1 Delay | Alarm 1 delay, 0-10 min (default 2) | min | Write | |
| AV | 8 | Alarm2 Setpoint | Alarm/relay 2 level (default 150 ppm CO or 4 ppm NO2) | ppm | Write | |
| AV | 9 | Alarm2 Hysteresis | Alarm 2 hysteresis (default 20 ppm CO or 0.5 ppm NO2) | ppm | Write | |
| AV | 10 | Alarm2 Delay | Alarm 2 delay, 0-10 min (default 2) | min | Write | |
| AV | 11 | Test Mode Time | Test mode duration, 1-15 min (default 5) | min | Write | |
| AV | 12 | CO Fault Mode Time | CO sensor-life timer, 3-6 years (default 3) | years | Write | |
| AV | 13 | NO2 Fault Mode Time | NO2 sensor-life timer, 1-4 years (default 2) | years | Write | |
| AV | 14 | CO ReCal Mode Time | CO recalibration reminder, 1-3 years (default 1) | years | Write | |
| AV | 15 | NO2 ReCal Mode Time | NO2 recalibration reminder, 1-3 years (default 1) | years | Write | |
| AV | 16 | Temperature Offset | Temperature offset, ±5 Δ°C or ±10 Δ°F (default 0) | delta °C / °F | Write | |
| AV | 17 | CO Strobe Setpoint | CO strobe level, 20-500 ppm (default 150) | ppm | Write | |
| AV | 18 | CO Strobe Delay | CO strobe delay, 0-10 min (default 5) | min | Write | |
| AV | 19 | NO2 Stobe Setpoint | NO2 strobe level, 1-10 ppm (default 2) | ppm | Write | |
| AV | 20 | NO2 Strobe Delay | NO2 strobe delay, 0-10 min (default 5) | min | Write | |
| BV | 1 | Buzzer Alarm | Buzzer master enable (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 2 | CO Buzzer Alarm | Buzzer on CO alarm (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 3 | NO2 Buzzer Alarm | Buzzer on NO2 alarm (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 4 | Buzzer Alarm Test | Buzzer test | Write | 0=Normal, 1=Test | |
| BV | 5 | Alarm1 Assignment | Gas that drives alarm 1 | Write | 0=CO, 1=NO2 | |
| BV | 6 | Alarm2 Assignment | Gas that drives alarm 2 | Write | 0=CO, 1=NO2 | |
| BV | 7 | Alarm Mode Operation | Alarm 1/2 reset mode (default Auto) | Write | 0=Auto Reset, 1=Manual Reset | |
| BV | 8 | Relay1 Operation | Relay 1 action | Write | 0=Direct, 1=Reverse | |
| BV | 9 | Relay2 Operation | Relay 2 action | Write | 0=Direct, 1=Reverse | |
| BV | 10 | Relay1 Test | Relay 1 test | Write | 0=Normal, 1=Test | |
| BV | 11 | Relay2 Test | Relay 2 test | Write | 0=Normal, 1=Test | |
| BV | 12 | Test Mode Enable | Starts test mode | Write | 0=Disable, 1=Enable | |
| BV | 13 | CO Fault Mode Enable | CO sensor-life alarm enable (default 0) | Write | 0=Disable, 1=Enable | |
| BV | 14 | CO Fault Mode Reset | Reset CO fault mode and timer | Write | 0=Normal, 1=Reset | |
| BV | 15 | NO2 Fault Mode Enable | NO2 sensor-life alarm enable (default 0) | Write | 0=Disable, 1=Enable | |
| BV | 16 | NO2 Fault Mode Reset | Reset NO2 fault mode and timer | Write | 0=Normal, 1=Reset | |
| BV | 17 | CO ReCal Mode Enable | CO recal reminder enable (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 18 | CO ReCal Mode Reset | Reset CO recal reminder and timer | Write | 0=Normal, 1=Reset | |
| BV | 19 | NO2 ReCal Mode Enable | NO2 recal reminder enable (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 20 | NO2 ReCal Mode Reset | Reset NO2 recal reminder and timer | Write | 0=Normal, 1=Reset | |
| BV | 21 | CO Zero Filter | CO zero filter (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 22 | NO2 Zero Filter | NO2 zero filter (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 23 | Strobe Alarm | Strobe master enable (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 24 | CO Strobe Alarm | Strobe on CO alarm (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 25 | NO2 Strobe Alarm | Strobe on NO2 alarm (default 1) | Write | 0=Disable, 1=Enable | |
| BV | 26 | Strobe Alarm Test | Strobe test | Write | 0=Normal, 1=Test | |
| BI | 1 | CO Sensor Status | CO sensor fitted | Read | 0=No Sensor, 1=Sensor | |
| BI | 2 | NO2 Sensor Status | NO2 sensor fitted | Read | 0=No Sensor, 1=Sensor | |
| BImin | 3 | Device Status | General device alarm | Read | 0=Normal, 1=Alarm | |
| BI | 4 | Buzzer Status | Buzzer sounding | Read | 0=Normal, 1=Alarm | |
| BImin | 5 | Alarm1 Status | Alarm/relay 1 active | Read | 0=Normal, 1=Alarm | |
| BImin | 6 | Alarm2 Status | Alarm/relay 2 active | Read | 0=Normal, 1=Alarm | |
| BI | 7 | Test Mode Status | Test mode running | Read | 0=Normal, 1=Test Mode | |
| BImin | 8 | CO Fault Mode Status | CO sensor-life fault | Read | 0=Normal, 1=CO Fault Mode | |
| BImin | 9 | NO2 Fault Mode Status | NO2 sensor-life fault | Read | 0=Normal, 1=NO2 Fault Mode | |
| BI | 10 | CO ReCal Mode Status | CO recalibration due | Read | 0=Normal, 1=CO ReCal Mode | |
| BI | 11 | NO2 ReCal Mode Status | NO2 recalibration due | Read | 0=Normal, 1=NO2 ReCal Mode | |
| BI | 12 | Strobe Status | Strobe active | Read | 0=Normal, 1=Alarm | |
| MV | 1 | LCD Format | Values shown on the LCD (default 1) | Write | 1=CO, 2=NO2, 3=CO + NO2, 4=Temp, 5=CO + Temp, 6=NO2 + Temp, 7=Status, 8=None | |
| MV | 2 | LCD Backlight | LCD backlight mode (default Auto) | Write | 1=Auto, 2=Off, 3=On |
No points match these filters.
Object ID lookup: Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 point IDs by name
AI1CO Sensor ValueAI2NO2 Sensor ValueAI3Temperature Sensor ValueAV1CO Buzzer SetpointAV2CO Buzzer DelayAV3NO2 Buzzer SetpointAV4NO2 Buzzer DelayAV5Alarm1 SetpointAV6Alarm1 HysteresisAV7Alarm1 DelayAV8Alarm2 SetpointAV9Alarm2 HysteresisAV10Alarm2 DelayAV11Test Mode TimeAV12CO Fault Mode TimeAV13NO2 Fault Mode TimeAV14CO ReCal Mode TimeAV15NO2 ReCal Mode TimeAV16Temperature OffsetAV17CO Strobe SetpointAV18CO Strobe DelayAV19NO2 Stobe SetpointAV20NO2 Strobe DelayBV1Buzzer AlarmBV2CO Buzzer AlarmBV3NO2 Buzzer AlarmBV4Buzzer Alarm TestBV5Alarm1 AssignmentBV6Alarm2 AssignmentBV7Alarm Mode OperationBV8Relay1 OperationBV9Relay2 OperationBV10Relay1 TestBV11Relay2 TestBV12Test Mode EnableBV13CO Fault Mode EnableBV14CO Fault Mode ResetBV15NO2 Fault Mode EnableBV16NO2 Fault Mode ResetBV17CO ReCal Mode EnableBV18CO ReCal Mode ResetBV19NO2 ReCal Mode EnableBV20NO2 ReCal Mode ResetBV21CO Zero FilterBV22NO2 Zero FilterBV23Strobe AlarmBV24CO Strobe AlarmBV25NO2 Strobe AlarmBV26Strobe Alarm TestBI1CO Sensor StatusBI2NO2 Sensor StatusBI3Device StatusBI4Buzzer StatusBI5Alarm1 StatusBI6Alarm2 StatusBI7Test Mode StatusBI8CO Fault Mode StatusBI9NO2 Fault Mode StatusBI10CO ReCal Mode StatusBI11NO2 ReCal Mode StatusBI12Strobe StatusMV1LCD FormatMV2LCD Backlight
Integration notes
- Points from the object table on pages 1-2 of the setup guide.
- Alarm 1/2 setpoint and hysteresis ranges change with BV 5/BV 6: CO 20-500 ppm, NO2 1-10 ppm.
- The table prints AV 19 as "NO2 Stobe Setpoint"; its object page spells it "NO2 Strobe Setpoint".
- Multistate objects are MSV in the guide; listed here as MV. Access from the PICS: AV, BV and MSV Present_Value are writable.
Check it against the live device. A points list tells you what the controller can expose; the unit in front of you may differ by firmware or installed options. This list is provided as-is for reference only and may contain mistakes — confirming it before you write, map or commission anything is up to you (terms). Easy BACnet scans a network for BACnet IP devices from an Android phone, reads every object on the GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP) and exports what it actually has to Excel — free. New to BACnet? Start with what a BACnet points list is and what the object types mean.
Questions about the Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP)
How many BACnet points does the Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP) have?
This list has 63 BACnet objects: 3 analog inputs, 20 analog values, 12 binary inputs, 26 binary values, 2 multi-state values. The exact set on a given unit depends on its firmware, installed options and configuration.
Which Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP) BACnet points are writable?
48 of the 63 objects accept a write. Points marked Command have a priority array: a write holds until it is released, so release it back to automatic when you are done.
Where is the official Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP) BACnet documentation?
The source is GDT Series Toxic Gas Detector - Setup Guide for BACnet Communication (SG-GDTXXXBAC-003), revision 2019-07-10 (PICS date), published free by Greystone Energy Systems at https://downloads.greystoneenergy.com/SG/SG-GDTXXXBAC-003.pdf.
What are the minimum BACnet points to integrate the Greystone Energy Systems GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP)?
Start with AI 1 CO Sensor Value (CO level, ppm); AI 2 NO2 Sensor Value (NO2 level, ppm); BI 5 Alarm1 Status (Alarm / relay 1 active (fan stage 1)); BI 6 Alarm2 Status (Alarm / relay 2 active (fan stage 2)); BI 3 Device Status (General device alarm); BI 8 CO Fault Mode Status (CO sensor end-of-life fault); BI 9 NO2 Fault Mode Status (NO2 sensor end-of-life fault).
How do I check these points on the real GDT Series toxic gas detector, CO / NO2 (BACnet MS/TP)?
Scan the network with a BACnet IP browser such as Easy BACnet, open the device and compare its object list with this table. Anything missing is usually an option that isn't installed or a point that is disabled in the controller's configuration.
More Greystone Energy Systems BACnet points lists
- CO2 sensor / transmitter
Greystone Energy Systems CDD3 Series CO2 transmitter (BACnet MS/TP)
Greystone CDD3 series room CO2 transmitters with the BACnet MS/TP output, with optional RH, temperature, relay and setpoint.
Also known as: CDD3, CDD3A1XXXBAC, CDD3 BACnet, Greystone CDD3 CO2 - CO2 / RH / temperature sensor
Greystone Energy Systems CHT Series CO2 / RH / temperature sensor (BACnet MS/TP)
Greystone CHT series combined CO2, humidity and temperature sensors with the BACnet MS/TP output.
Also known as: CHT, CHTDT, CHTXXXBAC, Greystone CHT - Carbon monoxide (CO) gas sensor / transmitter
Greystone Energy Systems CMD Series CO transmitter (BACnet MS/TP)
Greystone CMD series carbon monoxide transmitters (model name CMD5B) with BACnet MS/TP, with optional relays, buzzer and temperature.
Also known as: CMD, CMD5B, CMDXXXBAC, Greystone CMD carbon monoxide - Room temperature / RH / differential pressure monitor
Greystone Energy Systems CR3 Series cleanroom monitor (BACnet MS/TP)
Greystone CR3 series cleanroom and critical-room monitors measuring temperature, humidity and room differential pressure, with BACnet MS/TP.
Also known as: CR3, CR3XXXBAC, CR3C, Greystone CR3 critical room monitor - Room dewpoint / humidity sensor
Greystone Energy Systems DPRC Series room dewpoint transmitter (BACnet MS/TP)
Greystone DPRC series room dewpoint transmitters (PICS model DPRCB) with BACnet MS/TP.
Also known as: DPRC, DPRCB, DPRCXXXBAC, Greystone room dewpoint sensor - Duct / outdoor dewpoint and humidity sensor
Greystone Energy Systems DW Series duct / outside air dewpoint transmitter (BACnet MS/TP)
Greystone DW series duct and outside-air dewpoint transmitters (PICS models DPDDB and DPODB) and HTX2 high-accuracy RH/T transmitters with BACnet MS/TP.
Also known as: DW, DPDDB, DPODB, DWXXXBAC, Greystone duct dewpoint sensor, HTX2, HTX2XXXBAC, Greystone HTX2 high accuracy humidity transmitter - Greenhouse CO2 / RH / temperature sensor
Greystone Energy Systems GH Series horticulture sensor (BACnet MS/TP)
Greystone GH series horticulture (greenhouse / grow room) sensors measuring temperature, humidity and CO2, with BACnet MS/TP.
Also known as: GH, GHXXXBAC, Greystone greenhouse CO2 RH temperature sensor - Greenhouse CO2 sensor
Greystone Energy Systems GO3 Series horticulture CO2 sensor (BACnet MS/TP)
Greystone GO3 series horticulture CO2 sensors (0-20,000 ppm) with optional temperature, RH and relay, using BACnet MS/TP.
Also known as: GO3, GO3 BACnet, Greystone GO3 greenhouse CO2 - Humidity / temperature sensor
Greystone Energy Systems HN Series humidity / temperature transmitter (BACnet MS/TP)
Greystone HN series humidity and temperature transmitters with BACnet MS/TP and an optional relay.
Also known as: HN, HNXXXBAC, Greystone HN humidity sensor - Humidity / temperature sensor with condensation monitoring
Greystone Energy Systems HTX1 Series rough duty RH / temperature transmitter (BACnet MS/TP)
Greystone HTX1 series rough-duty RH/temperature transmitters (PICS model DP0011) with optional pipe-temperature condensation probe, digital input and relay, using BACnet MS/TP.
Also known as: HTX1, HTX1XXXBAC, DP0011, NPI-56, Greystone rough duty sensor - Indoor air quality multi-sensor (CO2 / PM / VOC / formaldehyde)
Greystone Energy Systems IAQRM Series multi-sensor (BACnet MS/TP)
Greystone IAQRM series room multi-sensors (PICS model MSN) measuring temperature, RH, CO2, VOC, particulates and formaldehyde, with BACnet MS/TP.
Also known as: IAQRM, MSN, IAQRMXXXBAC, Greystone indoor air quality multi sensor - Room temperature / humidity sensor
Greystone Energy Systems NTRC Series temperature / humidity room sensor (BACnet MS/TP)
Greystone NTRC series network room sensors (temperature, optional RH, setpoint, fan switch, override, relay and digital input) with BACnet MS/TP.
Also known as: NTRC, NTRCXXXBAC, STAT, Greystone NTRC network room sensor - Particulate matter (PM2.5 / PM10) sensor
Greystone Energy Systems PM Series particulate matter transmitter (BACnet MS/TP)
Greystone PM series particulate transmitters for room, duct and outdoor mounting (PMRMC, PMDT, PMOS) with BACnet MS/TP.
Also known as: PM Series, PMRMC, PMDT, PMOS, PMXXXBAC, Greystone particulate sensor - Room differential pressure sensor / monitor
Greystone Energy Systems RPC Series room pressure sensor (BACnet MS/TP)
Greystone RPC series room pressure monitors with local alarm buzzer and BACnet MS/TP.
Also known as: RPC, RPCXXXBAC, Greystone room pressure monitor - Ultra-low differential pressure sensor / transducer
Greystone Energy Systems UP Series ultra-low pressure transducer (BACnet MS/TP)
Greystone UP series ultra-low differential pressure transducers with BACnet MS/TP.
Also known as: UP, UPB, UPXXXBAC, Greystone ultra low differential pressure - VOC air quality sensor
Greystone Energy Systems VOC Series air quality transmitter (BACnet MS/TP)
Greystone VOC series room air quality transmitters (VOC with RH and temperature) with BACnet MS/TP and optional relay.
Also known as: VOC Series, VOCXXXBAC, Greystone VOC sensor, Greystone TVOC transmitter
Source: GDT Series Toxic Gas Detector - Setup Guide for BACnet Communication · SG-GDTXXXBAC-003 · rev. 2019-07-10 (PICS date). Object names, instances and units are reproduced as published; descriptions are our own.