What is a Fresh Air Ventilation System?

Fresh Air Ventilation System, in simple terms, is an air-circulation and exchange system that expels polluted indoor air to the outside while simultaneously drawing in fresh outdoor air. Through this continuous exchange, the indoor air is purified, thereby safeguarding human health.

Types Of Fresh-Air Ventilation Systems and Principles

Fresh-air Ventilation Systems are chiefly divided into three types: single-flow, dual-flow, and Total-heat-exchange systems.

A single-flow fresh-air system, such as an exhaust fan, removes indoor polluted air using a mechanical fan while relying on natural infiltration through gaps around doors and windows to allow fresh air in. A kitchen cooker hood can also be considered a single-flow fresh-air system.

Dual-flow fresh-air system uses two separate fans—one brings in filtered outdoor air under slight pressure while the other pushes out stale indoor air. A total-heat-exchange version adds a heat-exchange core between these two airflows. As stale air leaves, this core captures its warmth or coolness and passes it to the incoming air, so spend less energy heating or cooling fresh air and feel more comfortable.

How Does a Fresh Air Ventilation System Work?

Whichever type is used, the core operating principle remains the same: mechanical ventilation expels contaminated indoor air while filtering and purifying incoming air from outside, thus achieving a continuous cycle of indoor-outdoor air exchange. Such systems can effectively lower indoor concentrations of carbon monoxide, reduce harmful volatile organic compounds such as formaldehyde and benzene, as well as remove dust, pollen and other particulate matter—thereby providing occupants with a fresh, healthy indoor environment.

The Principal Functions of a Fresh-Air Ventilation System

1. Supply of fresh air. It can provide a continuous stream of fresh air to the interior 24/7 without opening windows, ensuring a natural and comfortable indoor ambiance.

2. Removal of toxic and odorous gases. It effectively eliminates cooking odors, tobacco smoke, exhaled carbon monoxide (CO) and other harmful Volatile organic compounds (VOCs), helping to protect elderly family members and children from the dangers of second-hand smoke.

3. Humidity control—preventing mold and musty odors. By expelling humid, stale air, it eradicates unpleasant smells and inhibits mold growth, thereby prolonging the lifespan of the building fabric and furnishings.

4. Reduction of noise pollution. There is no need to endure the disturbances that come with open windows, so the indoor environment remains quiet.

5. Dust prevention and pollen control—reduce allergens in home. The system reduces dust and allergens entering the home by using high-efficiency HEPA filters, which capture up to 99.97% of airborne particles as small as 0.3 micrometers, effectively alleviating triggers for respiratory allergies.

Application Scenarios

1. Residential areas

Fresh-air systems can operate continuously to safeguard the respiratory health of all household members.

2. Office buildings and other workspaces

In densely occupied environments, they enhance comfort and can even boost productivity.

3. Commercial spaces (hotels, shopping centers)

By creating a pleasant atmosphere, they improve the overall experience for visitors and raise the quality of the venue.

Whole House Air Ventilation System Carbon Monoxide

In modern life, people are increasingly attentive to indoor air quality. As a vital technology for improving that quality, fresh-air systems are becoming commonplace. Yet there is an invisible “killer” that can stealthily threaten our health and safety: carbon monoxide. An electrochemical carbon monoxide sensor is a key component within a fresh-air system, protecting us from this hazard.

What is Carbon Monoxide?

Carbon monoxide (CO) is a colorless, odorless, and highly toxic gas. In homes, if stoves or boilers aren’t ventilated properly, especially during winter, carbon monoxide concentrations can build up and reach lethal levels without any warning. The risk isn’t limited to residences: poultry houses and other livestock facilities that burn natural gas for heat can also generate dangerous CO when the fuel burns incompletely because of inadequate oxygen or faulty equipment.

To enhance safety, installing electrochemical CO sensors within the building’s air-ventilation system provides continuous, real-time monitoring; When concentrations increase, the system can automatically trigger alarms or enhance airflow, ensuring a safe environment for both people and animals.

The electrochemical sensor integrated into the whole-house air ventilation system effectively addresses this problem. According to UL 2034 standards, CO alarms must activate at 70 ppm within 1 to 4 hours and at 400 ppm within 4 to 15 minutes. However, an integrated ventilation system can respond much sooner when it continuously monitors CO levels.

By placing an electrochemical CO sensor in the supply or return duct, the fresh air unit can:

• Trigger audible and visible alarms
• Initiate high-speed purging
• Shut down the burner responsible for CO production
• Send alerts to building management system

All of these actions can be taken before residents are in danger.

Working Principle of an Electrochemical Carbon Monoxide Sensor

The electrochemical carbon monoxide sensor operates based on the basic principle of constant potential electrolysis. The sensor is mainly composed of a working electrode, a counter electrode, a reference electrode, and an electrolyte. When carbon monoxide gas diffuses through the gas permeable membrane to the surface of the working electrode, an oxidation reaction occurs under the action of the catalyst: CO+H2O → CO ₂+2H⁺+2e⁻, and the generated electrons flow to the counter electrode through the external circuit, while hydrogen ions (H ⁺) migrate to the counter electrode through the electrolyte. On the counter electrode, oxygen undergoes a reduction reaction: 1/2 O₂+2H ⁺+2e ⁻ → H2O. The current generated during this process is proportional to the concentration of carbon monoxide. The function of the reference electrode is to provide a stable potential reference, ensuring the stability of the working electrode potential, thereby making the measurement more accurate. By measuring the current in the circuit, the concentration of carbon monoxide can be accurately calculated.

Unique Advantages of Electrochemical CO Sensors

1. High sensitivity: The Electrochemical sensor can quickly and accurately detect extremely low concentrations of carbon monoxide (CO) in a short time, even when the CO levels in the air are just a few parts per million (ppm). This high sensitivity enables a fresh-air ventilation system for quick enhance airflow.

2. Good selectivity: The sensor exhibits high selectivity due to its working principle. In other words, electrochemical CO sensors can avoid interference from other gases. This ensures accurate readings of CO concentration without misjudgements caused by the presence of other indoor gases. Even in environments with small amounts of volatile gases, the sensor reliably detects carbon monoxide levels.

3. Linear output: All EURsense Electrochemical sensors supply linear correlation with target gas concentration, ensuring stable and reliable performance across diverse environments. This predictable response simplifies calibration and enables the fresh-air controller to regulate ventilation with precision and efficiency, even amidst fluctuating environmental conditions.

4. Long service life: Using advanced materials and processes, it has a long service life under normal use conditions, generally up to several years, reducing the cost and inconvenience caused by frequent replacement of sensors.

5. Good stability: The sensor maintains stable performance across a wide range of environmental conditions, including significant fluctuations in temperature and humidity. This stability ensures the accuracy and reliability of test results, allowing it to adapt to complex indoor environments, whether in the cold northern winters or the humid southern rainy seasons.

The Benefits of Using Carbon Monoxide Sensors in Fresh Air Systems

1. Real time monitoring to ensure safety

Integrating an electrochemical carbon monoxide sensor into a fresh air system is like installing a pair of sharp "eyes" on the fresh air system, which can monitor indoor carbon monoxide concentration in real time. Once the concentration exceeds the preset safety threshold, the sensor will immediately transmit a signal to the control unit of the fresh air system. After receiving the signal, the control unit will quickly activate the emergency mode, increase the fresh air exchange rate, and quickly exhaust the indoor air containing carbon monoxide from the outside. At the same time, more fresh air will be introduced to reduce the concentration of carbon monoxide, effectively preventing the occurrence of carbon monoxide poisoning incidents and safeguarding the safety of householders.

For example, a household installed a fresh air system equipped with an electrochemical carbon monoxide sensor. When a gas water heater malfunctioned and caused a slight leak, the sensor quickly detected an increase in carbon monoxide concentration. The fresh air system immediately ran at high speed and issued an alarm to remind family members to handle it in a timely manner, avoiding the tragedy.

2. Intelligent linkage enhances user experience

Combined with the intelligent control system of the fresh air system, the electrochemical carbon monoxide sensor can achieve more intelligent functions. For example, when the sensor detects an increase in carbon monoxide concentration, it can not only control the fresh air system to increase ventilation, but also link other intelligent devices, such as closing gas valves, to prevent the continued production of carbon monoxide; At the same time, by sending alert information to users through mobile apps, they can be informed of any abnormal situations at home in a timely manner and take corresponding measures no matter where they are. This intelligent linkage greatly enhances the safety and intelligence level of the home environment, allowing users to enjoy a more convenient and reassuring living experience.

Some high-end fresh-air ventilation products, such as the Panasonic Intelli-Balance® 200 ERV integrated with Swidget Wi-Fi Control and CO-sensor, come equipped with advanced electrochemical carbon monoxide sensors that seamlessly connect to popular smart home platforms, including Alexa, Google Home, and IFTTT. Users can conveniently manage their indoor air quality through voice commands, remotely control system operations via smartphone apps, and instantly access real-time carbon monoxide concentration data. This smart integration ensures consistent air quality monitoring and provides automatic ventilation adjustments whenever CO levels rise, keeping indoor environments safe, healthy, and comfortable.

Summary

Modern, highly insulated residential buildings offer comfort, privacy and energy efficiency, but they also trap exhaled carbon dioxide, water vapor, formaldehyde from furnishings and building materials, dust from fabrics, and odors from occupants, smoking and cooking. Simply opening a window often fails to provide satisfactory air exchange, temperature or humidity balance, and inadequate ventilation can lead to stale air, mold growth and even mite infestations. Consequently, a fresh-air system is essential to maintain indoor environmental quality.

Running such a system at full power can consume a lot of energy and may be noisy. Conversely, operating the fresh-air system at too low a power level may not exchange enough outdoor air to dilute or remove generated pollutants, leading to an accumulation of harmful substances like carbon monoxide (CO) from cooking, heating, smoking, or other combustion sources. Hence, it is vital to monitor indoor concentrations of CO and other gases in real time and to adjust the fresh-air system’s operation accordingly, balancing low energy use with occupant comfort.

For reliable, pre-calibrated carbon monoxide (CO) monitoring in fresh-air systems, the AG-4 EURsense Electrochemical sensors module is an excellent choice: The AG-4-CO-M5042(D) combines the AG-4 platform with Figaro's TGS5042 sensor. This module has been pre-calibrated at the factory and offers good stability and selectivity, making it ideal for use in building and industrial ventilation systems; the AG-4-CO-MCOAM(D) is an embedded module equipped with the Alphasense A series electrochemical CO-AM sensor, which is capable of detecting CO in various environments. With a compact 20 mm diameter. Its high accuracy is essential for ensuring safety, supporting medical applications, assessing air quality, and monitoring carbon monoxide levels in industrial settings. Key features of this sensor include high performance, a leak-free design, digital outputs (UART/TTL/RS232), and factory pre-calibration.