Ventilation Duct Temperature, Humidity and Particulate Matter Monitoring: Making Invisible Duct Environments Controllable

In industrial plants, commercial buildings, public facilities, and environmental protection projects, ventilation ducts play a critical role in air supply, exhaust, and regulation. However, duct interiors that remain enclosed for long periods are often high-risk areas with frequent temperature and humidity fluctuations and a tendency for pollutants to accumulate.

Ventilation duct temperature and humidity monitoring, together with online monitoring of particulate matter concentration inside ducts, is a key technical means for continuous perception and risk management of this “hidden environment.”

What Is Ventilation Duct Temperature and Humidity Monitoring

Ventilation duct temperature and humidity monitoring refers to the process of using dedicated duct temperature and humidity sensors to continuously, online, and recordably monitor air temperature (℃) and relative humidity (%RH) inside air ducts.

The core objectives include:

• Obtaining true environmental parameters inside air ducts

• Identifying conditions suitable for the growth of bacteria and mold

• Providing a basis for air-conditioning operation and air quality management

• Reducing the risk of secondary pollution

Unlike ordinary indoor monitoring, the duct interior environment is characterized by high airflow velocity, high dust levels, frequent vibration, and limited maintenance space, placing higher demands on monitoring equipment.

Why Ventilation Ducts Must Be Monitored for Temperature and Humidity

Air ducts are breeding grounds for pollutants and microorganisms
Supply air ducts contain not only dust but may also accumulate bacteria, fungi, and other microorganisms. Under suitable temperature and humidity conditions, these microorganisms can multiply rapidly.

Abnormal temperature and humidity amplify health risks
When air-conditioning systems start or ducts vibrate, pollutants attached to duct walls may enter indoor spaces with airflow, increasing the risk of respiratory diseases or sick building syndrome.

Experience-based management cannot support refined operation and maintenance
Without real-time data, maintenance personnel find it difficult to determine whether the duct interior environment remains in a high-risk state over time.

Why Dedicated Duct Temperature and Humidity Sensors Must Be Used

Limitations of ordinary temperature and humidity sensors
Ordinary sensors are often installed using drilled holes and probe plugs, which can easily cause air leakage, disrupt airflow structure, and affect measurement accuracy. They are also inconvenient for later maintenance and replacement.

Professional design of duct temperature and humidity sensors
Nexisense duct temperature and humidity sensors adopt a flange-mounted structure and are equipped with high-quality silicone sealing rings. While ensuring airtightness, the probe is stably inserted into the effective airflow area, avoiding measurement deviation.

Working Principle of Nexisense Duct Temperature and Humidity Sensors

The device has a built-in high-stability temperature and humidity measurement unit. Through a metal probe rod, it directly senses the airflow conditions inside the duct.

The collected analog signals are processed by internal circuitry and output as digital signals, which are then connected to monitoring systems or host computers via standard communication protocols.

Structural Analysis: Key Designs for Adapting to Complex Duct Environments

Measurement probe and protective structure
The probe adopts a stainless steel filter structure with a 25 μm high-density pore design, ensuring sufficient air exchange while effectively blocking dust and particulate matter.

Installation and sealing structure
The flange mounting method allows the device to fit tightly against the duct, reducing the impact of air leakage on system operation and measurement accuracy.

Anti-interference and protection design
The internal circuitry has strong electromagnetic interference resistance, enabling stable operation in industrial environments with strong interference sources such as frequency converters.

Display and on-site reading
A high-brightness color LED display alternately shows temperature and humidity data, facilitating on-site inspection.

Core Advantages of Duct Temperature and Humidity Monitoring

• Data directly sourced from inside the air duct

• Long-term stable operation with minimal drift

• Standardized installation without damaging airflow structure

• Easy integration with building management or environmental monitoring systems

• Support for multiple temperature range configurations

The Necessity of Online Particulate Matter Concentration Monitoring Inside Ducts

In industrial flues, dust removal ducts, and exhaust systems, particulate matter such as PM2.5 and PM10 is a major source of atmospheric pollution.

Continuous, online monitoring of particulate matter concentration is a critical foundation for emission control and environmental management.

Principle and Composition of Duct-Type Particulate Matter Monitoring Systems

Measurement principle
Based on the laser scattering principle, the system detects the scattering characteristics of particles when exposed to laser light. Combined with dual-frequency sampling and algorithm models, it calculates particulate matter mass concentration in μg/m³.

System composition

• Duct-type air quality transmitter (PM2.5 / PM10)

• RS485 communication network

• Environmental monitoring host

• 4G communication module

• Cloud monitoring platform

Typical Application Scenarios

• Central air-conditioning and fresh air systems

• Commercial buildings and public facility air ducts

• Industrial dust removal ducts and chimney flues

• Emission ducts in chemical, power, and metallurgical industries

Measurement Methods and Installation Key Points

• Temperature and humidity probes should be located in the main airflow area

• Avoid installation at bends, dead zones, or recirculation areas

• Ensure complete flange sealing

• Plan RS485 bus length and node quantity reasonably

Operation, Maintenance, and Care Recommendations

• Regularly check the condition of the stainless steel filter

• Clean surface dust to prevent long-term condensation

• Perform periodic calibration as required

• Check communication and alarm functions for normal operation

Frequently Asked Questions (FAQ)

Why can’t indoor temperature and humidity data replace duct monitoring?
The duct interior environment differs significantly from indoor environments. Indoor data cannot reflect real duct risks.

Do duct temperature and humidity sensors affect airflow?
When installed according to specifications, their impact on airflow is minimal and does not change the system’s designed air volume.

Are the devices suitable for high-humidity or condensing environments?
The stainless steel filter and protective design enable long-term use in high-humidity conditions.

How many monitoring points are required for one duct?
This should be determined based on duct length, number of branches, and risk level. Key nodes are recommended to have dedicated monitoring points.

Is RS485 communication stable in industrial environments?
With proper wiring and terminal matching, RS485 offers strong anti-interference performance.

Can particulate matter monitoring data be used for environmental management?
Continuously recorded data can be used for operational analysis, emission trend evaluation, and environmental management.

Does the system support remote centralized management?
Through 4G communication and cloud platforms, centralized monitoring of multiple ducts and projects is supported.

Is post-installation maintenance costly?
With a simple structure and high stability, routine maintenance mainly involves inspection and cleaning.

Conclusion

Although the internal environment of ventilation ducts is invisible, it directly affects air quality, human health, and emission compliance.

By deploying Nexisense duct temperature and humidity sensors and online particulate matter concentration monitoring systems, originally uncontrollable duct environments can be transformed into data systems that are monitorable, analyzable, and manageable.

Against the backdrop of increasingly refined building operation and industrial environmental protection, duct environment monitoring is becoming an essential foundation for ensuring safe system operation and environmental quality.