Overview

Two gas detection in a single unit

Equipped with electrochemical method; ESF sensors x 2, supporting detection of 2 gases. Piping and wiring costs can be reduced by half.

Compatible with over 300 existing sensors

More than 300 reliable gas sensors from the previous model GD-70D series can be used directly with the GD-81D series, so there is no need to replace existing sensors just for the GD-81D.

Furthermore, the next generation “F sensor” lineup for the GD-81D enables the installation of two sensors in a single unit.

Quiet operation with minimal vibration

The new Riken RP-80 pump ensures smoother operation and more comfortable working environment.

Reduced Noise
Revised valve configuration
Reduced Vibration

Two diaphragms to cancel vibration
Reduced Pump-pulsation
Buffer provided inside chamber

Auto Flow Adjustment

Even when filter clogging or changes in atmospheric conditions cause a drop in flow rate, the GD-81D automatically adjusts the sampling flow to maintain stable gas detection.
This intelligent system ensures uninterrupted and reliable gas monitoring, even under changing conditions — helping protect both personnel and process safety without the need for manual readjustment.

Quick Connection

Quick connection design that allows for quick and secure piping connections without the need for conventional union fittings.
This simple push-in mechanism eliminates complex tightening work, reduces installation time, and minimizes the risk of leakage due to human error, such as under- or over-tightening of the coupling nut.

Remote Monitoring & Control

Operators can check detector status and adjust settings remotely from the upper monitoring system—no need to access the detector body directly.
This capability greatly improves convenience in locations where detectors are installed in hazardous or hard-to-reach areas.

Gases

Choice of three different sensor units

U sensor unit

Conventional sensor unit compatible with a lineup of more than 300 sensor types and boasting high reliability.

F sensor unit

The unit accommodates one new F sensor which features significantly enhanced self-diagnostic functions. Also supports CO2 (ppm to vol%) detection.

M sensor unit

Sensor unit that can accommodate two F sensors for toxic gases. Detects two different toxic gases simultaneously

Gas Name	Display name	Detection range	Alarm setpoints	ACGIH acceptable concentration (2025)
Ammonia	NH3	0 – 75 ppm	25 ppm / 50 ppm	25 ppm
Monomethylamine	MMtA	0 – 15 ppm	5 ppm / 10 ppm	5 ppm
Dimethylamine	DMA	0 (0.9) – 15 ppm	5 ppm / 10 ppm	5 ppm
Trimethylamine	TMA	0 – 15 ppm	5 ppm / 10 ppm	5 ppm
Diethylamine	DEA	0 (0.2) – 15 ppm	5 ppm / 10 ppm	5 ppm
Methylethylamine	EMA	0 – 15 ppm	5 ppm / 10 ppm	―
Fluorine	F2	0 – 3 ppm	1 ppm / 2 ppm	0.1 ppm
Hydrogen fluoride	HF	0 (0.4) – 1.5 ppm	0.5 ppm / 1 ppm	0.5 ppm
Chlorine	Cl2	0 – 0.3 ppm	0.1 ppm / 0.2 ppm	0.1 ppm
Hydrogen chloride	HCl	0 – 6 ppm	2 ppm / 4 ppm	2 ppm
Bromine	Br2	0 – 1 ppm	0.3 ppm / 0.6 ppm	0.1 ppm
Hydrogen bromide	HBr	0 – 6 ppm	2 ppm / 4 ppm	2 ppm
Chlorine trifluoride	ClF3	0 – 0.3 ppm	0.1 ppm / 0.2 ppm	0.1 ppm
Ozone	O3	0 – 0.6 ppm	0.2 ppm / 0.4 ppm	0.2 ppm (<2h)
Silane	SiH4	0 – 15 ppm	5 ppm / 10 ppm	5 ppm
Disilane	Si2H6	0 – 15 ppm	5 ppm / 10 ppm	―
Phosphine	PH3	0 – 0.15 ppm	0.05 ppm / 0.1 ppm	0.05 ppm
Diborane	B2H6	0 – 0.3 ppm	0.1 ppm / 0.2 ppm	0.1 ppm
Hydrogen cyanide	HCN	0 (0.9) – 15 ppm	4 ppm / 10 ppm	4.7 ppm
Germane	GeH4	0 – 0.8 ppm	0.2 ppm / 0.4 ppm	0.2 ppm
Arsine	AsH3	0 – 50 ppb	10 ppb / 20 ppb	0.005 ppm
Hydrogen selenide	H2Se	0 – 0.2 ppm	0.05 ppm / 0.1 ppm	0.05 ppm
Carbon monoxide	CO	0 – 75 ppm	25 ppm / 50 ppm	25 ppm
Nitrogen monoxide	NO	0 – 100 ppm	25 ppm / 50 ppm	25 ppm
Nitrogen dioxide	NO2	0 – 9 ppm	3 ppm / 6 ppm	0.2 ppm
Sulfur dioxide	SO2	0 – 6 ppm	2 ppm / 4 ppm	0.25 ppm
Nitrogen trifluoride	NF3	0 – 30 ppm	10 ppm / 20 ppm	10 ppm
Oxygen	O2	0 – 25 vol%	18 vol%/18 vol%	―
Hydrogen	H2	0 – 2,000 ppm	500 ppm / 1,000 ppm	―

Freon 41	R-41	0 – 2,000 ppm	500 ppm / 1,000 ppm	―
Freon 32	R-32	0 – 2,000 ppm	500 ppm / 1,000 ppm	―
Isopropyl alcohol	IPA	0 – 2,000 ppm	500 ppm / 1,000 ppm	200 ppm
Ethylene	C2H4	0 – 2,000 ppm	500 ppm / 1,000 ppm	200 ppm
Propylene	C3H6	0 – 2,000 ppm	500 ppm / 1,000 ppm	500 ppm
Methane	CH4	0 – 5,000 ppm	2,000 ppm / 4,000 ppm	―
Perfluorobutadiene	C4F6	0 – 2,000 ppm	500 ppm / 1,000 ppm	―
Isobutane	i-C4H10	0 – 2,000 ppm	500 ppm / 1,000 ppm	1,000 ppm
Acetylene	C2H2	0 – 2,000 ppm	500 ppm / 1,000 ppm	―
Propane	C3H8	0 – 2,000 ppm	500 ppm / 1,000 ppm	―
Ethyl alcohol	C2H5OH	0 – 2,000 ppm	500 ppm / 1,000 ppm	1,000 ppm
Acetone	C3H6O	0 – 2,000 ppm	500 ppm / 1,000 ppm	250 ppm
Deuterium	D2	0 – 2,000 ppm	500 ppm / 1,000 ppm	―
Hydrogen	H2	0 – 2,000 ppm	500 ppm / 1,000 ppm	―
Methane	CH4	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Ethane	C2H6	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Propane	C3H8	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Isobutane	i-C4H10	0 – 100 %LEL	25 %LEL / 50 %LEL	1,000 ppm
Hydrogen	H2	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Toluene	C7H8	0 – 100 %LEL	25 %LEL / 50 %LEL	20 ppm
Acetone	C3H6O	0 – 100 %LEL	25 %LEL / 50 %LEL	250 ppm
Acetylene	C2H2	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Ethylene	C2H4	0 – 100 %LEL	25 %LEL / 50 %LEL	200 ppm
Ethyl alcohol	C2H5OH	0 – 100 %LEL	25 %LEL / 50 %LEL	1,000 ppm
Methyl alcohol	CH3OH	0 – 100 %LEL	25 %LEL / 50 %LEL	200 ppm
Propylene	C3H6	0 – 100 %LEL	25 %LEL / 50 %LEL	500 ppm
Vinyl chloride	VCM	0 – 100 %LEL	25 %LEL / 50 %LEL	1 ppm
Methane	CH4	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Ethylene	C2H4	0 – 100 %LEL	25 %LEL / 50 %LEL	200 ppm
Toluene	C7H8	0 – 100 %LEL	25 %LEL / 50 %LEL	20 ppm
Propylene	C3H6	0 – 100 %LEL	25 %LEL / 50 %LEL	500 ppm
Acetone	C3H6O	0 – 100 %LEL	25 %LEL / 50 %LEL	250 ppm
Benzene	C6H6	0 – 100 %LEL	25 %LEL / 50 %LEL	0.02 ppm
Freon 32	R-32	0 – 20,000 ppm	5,000 ppm / 10,000 ppm	―
Freon 41	R-41	0 – 20,000 ppm	5,000 ppm / 10,000 ppm	―
Propane	C3H8	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Isobutane	i-C4H10	0 – 100 %LEL	25 %LEL / 50 %LEL	1,000 ppm
Ethane	C2H6	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Normal butane	n-C4H10	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Methyl alcohol	CH3OH	0 – 100 %LEL	25 %LEL / 50 %LEL	200 ppm
Ethyl alcohol	C2H5OH	0 – 100 %LEL	25 %LEL / 50 %LEL	1,000 ppm
Isopropyl alcohol	IPA	0 – 100 %LEL	25 %LEL / 50 %LEL	200 ppm
Normal propyl alcohol	C3H8O	0 – 100 %LEL	25 %LEL / 50 %LEL	100 ppm
Tetrahydrofuran	THF	0 – 100 %LEL	25 %LEL / 50 %LEL	50 ppm
Methyl ethyl ketone	MEK	0 – 100 %LEL	25 %LEL / 50 %LEL	75 ppm
Ethyl acetate	EtAc	0 – 100 %LEL	25 %LEL / 50 %LEL	400 ppm
Methyl isobutyl ketone	MIBK	0 – 100 %LEL	25 %LEL / 50 %LEL	20 ppm
Dimethyl carbonate	C3H6O3	0 – 100 %LEL	25 %LEL /5 0 %LEL	―
Ethyl methyl carbonate	EMC	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Diethyl carbonate	C3H10O3	0 – 100 %LEL	25 %LEL / 50 %LEL	―
Nitrous oxide	N2O	0 – 500 ppm	50 ppm / 100 ppm	50 ppm
Carbon dioxide	CO2	0 – 2,000 ppm	1,000 ppm / 1,000 ppm	5,000 ppm
Carbon dioxide	CO2	0 – 100 vol%	25 vol%/50 vol%	5,000 ppm
Ammonia	NH3	0 – 75 ppm	25 ppm / 50 ppm	25 ppm
Dimethylamine	DMA	0 (0.2) – 15 ppm	5 ppm / 10 ppm	5 ppm
Fluorine	F2	0 – 3 ppm	1 ppm / 2 ppm	0.1 ppm
Hydrogen fluoride	HF	0 (0.4) – 1.5 ppm	0.5 ppm / 1 ppm	0.5 ppm
Chlorine	Cl2	0 – 0.3 ppm	0.1 ppm / 0.2 ppm	0.1 ppm
Chlorine	Cl2	0 – 1.5 ppm	0.5 ppm / 1 ppm	0.1 ppm
Hydrogen chloride	HCl	0 – 6 ppm	2 ppm / 4 ppm	2 ppm
Hydrogen bromide	HBr	0 – 6 ppm	2 ppm / 4 ppm	2 ppm
Chlorine trifluoride	ClF3	0 – 0.3 ppm	0.1 ppm / 0.2 ppm	0.1 ppm
Ozone	O3	0 – 0.6 ppm	0.2 ppm / 0.4 ppm	0.2 ppm (<2h)
Silane	SiH4	0 – 15 ppm	5 ppm / 10 ppm	5 ppm
Phosphine	PH3	0 – 1 ppm	0.3 ppm / 0.6 ppm	0.05 ppm
Monomethylsilane	CH3SiH3	0 – 20 ppm	5 ppm / 10 ppm	―
Nitrogen monoxide	NO	0 – 100 ppm	25 ppm / 50 ppm	25 ppm
Nitrogen dioxide	NO2	0 – 15 ppm	5 ppm / 10 ppm	0.2 ppm
Sulfur dioxide	SO2	0 – 6 ppm	2 ppm / 4 ppm	0.25 ppm
Hydrogen	H2	0 – 2,000 ppm	500 ppm / 1,000 ppm	―
Methane	CH4	0 – 100 %LEL	25 %LEL / 50 %LEL	―

Specifications

Model	GD-81D	GD-81D-ETD
Detection principles	Catalytic combustion type (NCF, NCU) / semiconductor type (SGF, SGU) / hot-wire semiconductor type (SHF, SHU) / Electrochemical type (ESF, ESU, M sensor1) / galvanic cell type (OSU) / infrared type (IRF, IRU) / pyrolysis-particle type (SSU)2
Detection target gas	Combustible gas, toxic gas, oxygen, carbon dioxide, etc.
Concentration display	Full-dot display
Detection method	Pump suction (approx. 0.5 L/min)
Power supply indication	POWER lamp lit (green)
Display items	Gas name display, flow rate display, mode display, pyrolyzer connection display*3
Gas alarm type	Two-step alarm (H-HH) / Oxygen (ESU) sensor: two-step alarm (L-LL) / Oxygen (OSU) sensor: two-step alarm (L-LL, L-H, H-HH)
Gas alarm indication	First alarm: ALM1 lamp lit (red), second alarm: ALM2 lamp lit (red)
Gas alarm pattern, fault alarm pattern*4	Auto reset / self-latching
Gas alarm contact, fault alarm contact*5	No-voltage contact 1a/1b (for ALM1/ALM2/Fault) Always de-energized (energized in alarm state) or always energized (de-energized in alarm state)
Fault alarm / self-diagnosis	System abnormality, sensor abnormality, flow abnormality, communication abnormality, pyrolyzer abnormality
Fault alarm indication	FAULT lamp lit (yellow), information display
Contact capacity	24 V DC, 0.5 A (resistance load)
Contact cable	1.25 mm² (AWG16) cable, max. 6-core
Transmission method	3-wire analog transmission (common power and signal) / 2-wire analog transmission	Ethernet (10BASE-T / 100BASE-TX)
Transmission cable	Shielded cable 1.25 mm2 (AGW16), 3-core/2-core	Category 5 or better Ethernet cable
Power supply	24 V DC ± 10 %	24 V DC ± 10 % / PoE
Power supply cable	1.25 mm² (AWG16) cable, 2-core (Not required for 3-wire analog transmission)	1.25 mm² (AWG16) cable, 2-core (Not required for PoE connection)
Power consumption For ESU/ESF sensors*6	Approx. 1.5 W, max. 4.0 W	24 V DC: 2.5 W, max. 4.5 W PoE: 3.5 W, max. 6.5 W
Tube connecting ports	One-touch quick connect coupler, PTFE tube O.D. 6 × I.D. 4 mm (1/4 × 1/8 in) / (1/4 × 3/16 in)
Functions	White backlight, alarm delay, suppression, zero follower, sensitivity correction, flow control, adjustment history, alarm trend history, event history
Initialization	Approx. 25 seconds
Temperature / humidity range*6	-10 °C to +40 °C (14 °F to 104 °F) (no sudden fluctuations), 0 to 95 %RH (no condensation)
Construction, exterior color	Wall-mounted type, main unit: black, front door: white
External dimensions, weight	Approx. 70 (W) × 120 (H) × 145 (D) mm (approx. 2.76 × 4.72 × 5.71 in), approx. 0.8 kg (approx. 1.76 lb)

Download

GD-81D Literature
GD-81D Datasheet

GD-81D Manuals
GD-81D Operator’s Manual

GD-81D Software
GD-81D Maintenance

Distributor Resources

GD-81D Price List & Resources
(Authorized Distributors Only)

GD-81D Sample Draw Gas Sensor

Sample Draw Gas Detector

Features