Why is Hopcalite Catalyst Needed in Tunnel Ventilation Systems?

In the semi-enclosed spaces of tunnels, vehicle exhaust accumulates, creating an invisible threat. However, a catalytic material called hopcalite is quietly protecting the safety of every occupant.
Tunnels are a vital component of modern transportation networks, yet the air quality within them is rarely considered. Vehicle exhaust accumulates in this enclosed space, forming high concentrations of pollutants, among which carbon monoxide (CO) is the most threatening invisible killer.
This colorless and odorless gas can bind to hemoglobin, leading to tissue hypoxia and, in severe cases, even life-threatening conditions. Hopcalite catalysts have become a key protective technology in tunnel ventilation systems to address this challenge.

The Invisible Threat in Tunnel Air

Air pollution inside tunnels primarily comes from vehicle exhaust emissions. Within this enclosed space, pollutants are difficult to disperse, and concentrations quickly rise to dangerous levels.
According to the Technical Regulations for Highway Construction Safety, carbon monoxide concentrations in tunnels must be controlled below 30 mg/m³. However, during peak traffic hours or in poor ventilation conditions, this limit can easily be exceeded.
In addition to carbon monoxide, tunnel air also contains harmful gases such as nitrogen oxides, sulfur dioxide, and hydrogen sulfide. These pollutants collectively pose a serious threat to the health of pedestrians and workers.
Long-term exposure to these pollutants can cause respiratory diseases, neurological damage, and even cancer. Therefore, effectively controlling tunnel air quality has become a critical issue in modern transportation construction.

How Hopcalite Works

Hopcalite is an oxidation catalyst made from activated manganese dioxide and copper oxide in a specific ratio. Its unique feature is its ability to efficiently catalyze the oxidation of carbon monoxide at room temperature and pressure.
This process requires no external heating or special pressure conditions, making it particularly suitable for the practical application environment of tunnel ventilation systems.
When air containing CO passes through the hopcalite, the catalyst absorbs and activates oxygen from the surrounding air, converting the toxic carbon monoxide into relatively harmless carbon dioxide.
Compared to precious metal catalysts, hopcalite exhibits significantly higher carbon monoxide oxidation activity at room temperature. This characteristic gives it a distinct advantage in tunnel ventilation, where large volumes of air must be processed and temperature fluctuations are minimal.

Technical Advantages and Limitations

The most significant advantage of hopcalite lies in its combination of high activity and low cost. This catalyst can operate at room temperature, requiring no additional energy input to maintain the reaction temperature, significantly reducing operating costs.
Furthermore, hopcalite's primary component is a transition metal oxide, which is widely available and has a relatively simple preparation process, making it significantly less expensive than precious metal catalysts such as platinum and palladium. However, hopcalite also has a significant limitation: it is highly sensitive to moisture. When ambient humidity exceeds 45%, the catalyst rapidly becomes "poisoned" and deactivated.
This characteristic poses a significant challenge in humid tunnel environments. Furthermore, the catalyst is less effective at treating low concentrations of carbon monoxide than precious metal catalysts.

Key Points for Tunnel Applications

Successful application of hopcalite in tunnel ventilation systems requires addressing its sensitivity to water. In practical applications, a high-efficiency desiccant is typically installed before the catalyst.
This pretreatment step removes excess moisture from the air, ensuring the catalyst operates at an appropriate humidity.
System design should adopt an intermittent operation strategy rather than continuous catalyst operation. When the sensor detects that the carbon monoxide concentration has dropped to a safe range, the catalyst layer should be temporarily bypassed to reduce its exposure to humid air.
An accurate monitoring system is also required. Traditional electrochemical CO sensors may be affected by interference from other gases in the tunnel, resulting in false alarms. Infrared CO sensors are recommended for more accurate data.
Regular replacement of desiccant and catalyst is also crucial, and a sound maintenance plan should be established to ensure long-term and effective system operation.

Future Development Trends

As tunnel safety requirements continue to increase, hopcalite catalyst technology is continuously improving. Integration with intelligent ventilation systems is another development direction. By combining hopcalite catalyst modules with real-time air quality monitoring systems, ventilation strategies can be automatically adjusted based on tunnel traffic volume and pollutant concentrations, achieving dual optimization of safety and energy efficiency.
New material exploration is also ongoing. Scientists are studying the possibility of loading hopcalite onto various nanoporous materials to increase their specific surface area and active sites, further improving catalytic efficiency and resistance to poisoning.
With the continued growth of urban tunnel construction, the intelligentization of ventilation systems has become an inevitable trend. In the future, new purification modules integrating hopcalite will be deeply integrated with intelligent monitoring systems to achieve precise control of tunnel air quality.
This technology approach is not only applicable to traffic tunnels but can also be expanded to various semi-enclosed spaces such as underground parking lots and underground utility corridors, providing safety assurance for urban underground space development. Advances in tunnel environmental control technology represent our continued commitment to improving urban infrastructure safety standards and demonstrate the respect and protection that engineering technology provides for life and health.

Author: Hazel
Date: 2025-09-23