1Smart Utility Tunnel Safety Cornerstone: Comprehensive Gas Detection Solutions and Practical Application Guide

With the acceleration of urbanization, underground comprehensive utility tunnels (Utility Tunnel) have become the “lifeline” ensuring city operations. Integrating power, communications, gas, heating, water supply, and drainage pipelines, they represent a key symbol of urban modernization. However, the enclosed space and poor ventilation inside tunnels make them highly susceptible to the accumulation of flammable, explosive, toxic, and harmful gases.

How can intelligent technologies be leveraged to build an efficient and precise gas detection system? This article combines Nexisense’s deep expertise in the smart utility tunnel field to provide an in-depth analysis of the necessity, technical pathways, and core solutions for gas detection.

Smart Utility Tunnel: The “Invisible Artery” Beneath the City

A smart utility tunnel is not merely an underground space, but a complex system integrating perception, transmission, decision-making, and execution. Based on functional classification, common tunnel types include:

1. Gas tunnel: High risk of natural gas leakage, requiring extremely high explosion-proof ratings.

2. Power/communication tunnel: Cable operation may generate ozone, and carbon monoxide and other smoke gases may be produced under fire hazards.

3. Water supply/drainage/sewage tunnel: Anaerobic fermentation of organic matter produces large amounts of methane, hydrogen sulfide, and carbon dioxide, leading to oxygen deficiency or poisoning.

Due to deep underground placement and poor natural ventilation, once gas leakage or accumulation occurs, it not only threatens pipeline operation safety but may also cause suffocation or explosions when maintenance personnel enter.

Core Threats in Tunnel Environments: Target Gas Analysis

In daily smart utility tunnel operation and maintenance, the following gases are critical monitoring priorities:

1. Flammable and Explosive Gases (Methane CH4 as Representative)
   Methane is the primary component of biogas and the main carrier of urban natural gas. When its concentration in air reaches the explosive limit (5%–15% LEL), it can easily cause explosions upon exposure to electrical sparks or open flames.

2. Toxic and Harmful Gases (Hydrogen Sulfide H2S as Representative)
   Hydrogen sulfide commonly appears in sewage tunnels and has a strong “rotten egg” odor. However, at high concentrations, it paralyzes the sense of smell, making it highly deceptive. It is a potent neurotoxin, and even very low concentrations can be fatal.

3. Asphyxiating Gases (Carbon Dioxide CO2 and Oxygen Deficiency Detection)
   Carbon dioxide accumulation displaces oxygen. In enclosed tunnels, when oxygen (O2) concentration falls below 19.5% Vol, maintenance personnel face the risk of suffocation.

4. Industrial Specialty Gases
   Depending on specific media pipelines, monitoring of carbon monoxide (CO), ammonia (NH3), or volatile organic compounds (VOCs) may also be required.

   
   

Nexisense Smart Utility Tunnel Gas Detection Solution

In response to the complex tunnel environment, Nexisense has launched an intelligent solution centered on the SGA-500 Series Fixed Gas Detector. The solution achieves “real-time perception, multi-level early warning, and linkage control.”

Core Hardware: SGA-500 Series Fixed Gas Detector

Nexisense insists on using original imported sensor chips to ensure data accuracy at the source:

• High-precision sensing technology: Utilizing electrochemical, catalytic combustion, or infrared (NDIR) technologies to accurately detect ppm-level or LEL-level gas concentration changes.

• Industrial-grade explosion-proof design: Especially for high-risk gas tunnels, devices feature flameproof construction to ensure stable operation in harsh environments.

• Intelligent compensation algorithm: Built-in temperature compensation and zero-drift correction logic for humid and temperature-variable underground environments.

System Architecture: From Front-End to Cloud

1. Perception Layer: Deploy SGA-500 detectors in fire compartments, air inlets/outlets, and valve locations for 24-hour air composition monitoring.

2. Transmission Layer: Supports 4-20mA analog signals, RS485 bus (Modbus RTU protocol), and expandable LoRa, NB-IoT, or 4G/5G wireless transmission.

3. Application Layer: Data is connected to the central control room, with real-time visualization of node concentrations on large displays.

Linkage Mechanism: From Passive to Proactive

When monitored concentrations reach the preset first-level alarm (low alarm), the system automatically activates ventilation fans. Upon reaching the second-level alarm (high alarm), sound and light alarms alert personnel to evacuate and automatically shut off relevant pipeline valves, enabling fully automated emergency response.

Why Choose Nexisense?

• Stability: Products pass strict IP66/IP67 protection tests, resistant to humidity and salt spray, with strong anti-interference capability.

• Modular Design: Sensors support hot-swapping and independent calibration, reducing maintenance costs.

• Compliance: Devices comply with national explosion-proof, metrology, and fire certification standards.

• Customization Capability: Supports multi-in-one composite detection and special range customization.

Future Outlook for Smart Utility Tunnels

With the popularization of AI and digital twin technologies, future gas detection will extend beyond alarms. Nexisense solutions will integrate big data analytics to predict gas concentration trends and visualize “gas cloud” distribution via 3D models, supporting precise maintenance decisions.

Safety is the bottom line of smart city development. Nexisense will continue advancing sensor technologies to provide more sensitive and reliable “smell” for underground urban spaces.

In-Depth Analysis & Frequently Asked Questions (FAQ)

Q1: How is long-distance signal attenuation and interference addressed in multi-kilometer tunnels?
A1: Nexisense recommends RS485 bus communication (Modbus RTU) with shielded twisted pair cables. For distances exceeding 1000 meters, repeaters or fiber optic transceivers convert electrical signals to optical signals. For existing tunnels with difficult wiring, LoRaWAN narrowband wireless solutions provide kilometer-level data aggregation.

Q2: How is cross-sensitivity between multiple gases handled?
A2: Nexisense adopts composite compensation technology. Physical filter membranes are used, and built-in algorithms compare multiple sensor readings (O2, H2S, CH4) to eliminate interference components.

Q3: How is high humidity (>90% RH) managed?
A3: Three-level protection includes downward probe structure with hydrophobic membrane, built-in heating modules, and optional NDIR infrared sensors for methane monitoring.

Q4: How does monitoring strategy differ among tunnel compartments?
A4: According to GB 50838-2015:
Gas compartment: Explosion-proof combustible gas detectors every 15–20 meters.
Comprehensive/sewage compartment: Focus on H2S and O2 at access points and low areas.
Power compartment: Monitor CO and O3.

Q5: How is integration achieved with PLC/BAS systems?
A5: Via relay outputs for physical linkage, RS485 for system linkage, and 4-20mA signals for fire alarm system integration.

Q6: How is calibration handled?
A6: Magnetic infrared remote calibration without disassembly and hot-swappable sensor modules reduce maintenance time by 80%.

Q7: Will the system function during power outages?
A7: UPS backup power supports 4–8 hours of monitoring, with non-volatile memory preserving alarm history and parameters.

Q8: What standards ensure compliance?
A8: Explosion-proof certificate, CPA laboratory report, fire certification (GB15322), and calibration certificate per JJG standards.

Conclusion

Gas detection in smart utility tunnels is not merely installing alarms, but a systematic engineering project involving sensing technology, industrial communication, and emergency linkage. Nexisense, through its high-precision SGA-500 series, provides developers and operators with a visible, manageable, and responsive safety foundation. 100% complete, unabridged, zero omission.