Basic requirements:
General characteristics:
Portable, portable.
With a built-in pump.
Withstand a fall from a height of at least 3 meters.
Work for at least 30 hours on a single charge.
Ergonomic two-button design.
Measured gases and ranges:

Oxygen (O2): 0-40 vol. % (measurement step 0.1%).
Carbon monoxide (CO): 0-2300 mg/m3 (measuring step 1 mg/m3).
Hydrogen sulfide (H2S): 0-280 mg/m3 (measuring step 0.1 mg/m3).
Methane (CH4): 0-100% NSAIDs (1% measurement step).
Type of sensors:

Electrochemical (O2, CO, H2S).
Thermocatalytic (CH4).
Sampling parameters:

The forced method is using the built-in pump.
The pump flow rate is not less than 0.35 l/min.
Sampling from a distance of at least 30 m.
Alarm system:

Vibration, visual, sound (volume 95 dB at a distance of 30 cm).
Two alarm thresholds with indication via red LEDs, flickering concentration value, continuous sound alert, vibration.
Food:

Lithium-ion battery.
Fast charging: Up to 90% in 3 hours.
Operational parameters:

Temperature: -40 to +60 (temporarily), -20 to +50 (continuously).
Humidity: 0-95% relative humidity (non-condensing).
Physical characteristics:

Dimensions: At least 173 × 64 × 47 mm (without bulging parts).
Weight: 280 g (with pump).
Built-in flashlight.
Data transmission:

An infrared port for communication with a PC.
Additional functions:

Self-locking in case of malfunctions (sensor, battery, system, calibration).
Fault indication via flickering lamps, intermittent beep, information on the screen.
Equipment:

The gas analyzer.
The charger.
An 8 m hose with a float resistant to aggressive environments.
Rubber cover.
Bag (without contents).
The manual is in Russian.
Warranty and year of manufacture:

Sensor warranty: 36 months.
Year of release: Not earlier than 2024.