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Digital display instruments: http://yunrun.com.cn/product/ As global industrialization progresses, environmental air pollution worsens, and humanity’s desire for a healthy living environment grows stronger... In this context, machine-based sensing capabilities, which represent an extension of the human sense of smell, have seen tremendous opportunities for development. The origin of machine olfaction: the birth of gas sensors. Machine olfaction is a novel biomimetic detection technology that simulates the working principle of biological olfaction. A machine olfaction system typically consists of a cross-sensitive array of chemical sensors along with appropriate computer-based pattern recognition algorithms, and it can be used to detect, analyze, and identify various odors. Gas sensors play the key role in a machine’s sense of smell, as odor is an external characteristic of substances. By detecting odors, gas sensors can accurately obtain information about these substances, converting the volume fractions of various gases into corresponding electrical signals to generate relevant data. The development of gas sensors dates back to over 50 years ago; gas detectors were invented in the 1960s. Wickens and Hatman developed gas detectors by utilizing the redox reactions of gases at electrodes; later, in the 1980s, Persaud and others in the UK proposed using gas detectors to simulate biological olfaction, which marked the beginning of gas sensors. It was not until the 1970s that the theory of gas sensors was introduced to our country. In the 1980s, China began developing gas sensors, with the entire technology being primarily inherited from Germany. Subsequently, with the development and use of various types of natural gas, coal-derived gas, and liquefied gas, domestic and international efforts were intensified to study detection and control methods for combustible gases. As a result, a variety of sensors and instruments for gas detection and analysis were developed, which are widely used in gas detection and composition analysis in industrial and daily life. As an extension of the human sense of smell, gas sensors are essential components for detecting air and the environment. Today, gas sensors are widely used in industries such as manufacturing, healthcare, environmental protection, and the chemical industry. In recent years, they have been rapidly adopted in consumer applications as well, experiencing explosive growth especially in the fields of environmental protection and health. Development of machine olfaction: Air pollution gives rise to various application scenarios for gas sensors. In the past, gas sensors were widely used in industrial settings, as many industrial gases are highly toxic and their leakage can pose a threat to human health; there are also flammable gases that present an explosion risk. Therefore, gas sensors can detect issues such as gas leaks as soon as possible, preventing safety problems from escalating to critical dangerous situations. Now, as industrial scale gradually expands and the variety of products increases, the types and quantities of gas raw materials as well as those generated during production processes keep rising. As a result, the scope of gas pollution is expanding rapidly, and the environment in which we live has been severely polluted; even our very existence is under threat. According to the World Health Organization’s 2016 global assessment on disease incidence and burden, air pollution is by far the greatest environmental risk to health; it can have adverse effects on the human body and even cause diseases. Approximately one in nine deaths each year are attributed to it, and only one in ten people live in cities that meet the World Health Organization’s air quality guidelines. Therefore, it is highly necessary to use machine olfaction technology to detect the air quality of the surrounding environment in advance, so as to improve and manage it and maintain human health. For example, corresponding gas sensors are used to detect acid rain gases/greenhouse gases, toxic gases such as formaldehyde, and PM 2.5, etc. The market for machine olfaction is undergoing significant changes today, driven primarily by a large number of consumer applications, which have given rise to various application scenarios for gas sensors. With the improvement of living standards and the growing awareness of environmental protection, there are higher demands for the detection of various toxic and harmful gases, for monitoring air pollution and industrial exhaust gases, as well as for testing the quality of food and living environments. For example, various smart home and wearable devices used in the Internet of Things can be employed to monitor the air quality of the surrounding environment or to improve it. Detection of harmful gases in indoor decorations: In over 90% of newly renovated homes, the levels of harmful gases are significantly above the allowed limits. Taking formaldehyde as an example, its concentration in newly finished homes is usually above 2.5 ppm, with some cases reaching levels of ten or even dozens of ppm. According to the GBT18883-2002 Standard for Indoor Air Quality, the maximum allowable level of formaldehyde is 0.1 mg/m3, which is equivalent to 0.074 ppm. By applying gas sensors to home environments, separate gas detection devices can be used to monitor volatile organic compounds such as formaldehyde, benzene, and toluene. Alternatively, gas sensors can be integrated with air conditioners, air fresheners, and air purifiers in order to combine indoor pollution detection with purification functions. This approach not only provides the best protection for vulnerable groups such as the elderly, the weak, women, and children who spend a lot of time at home, but also allows those who are working away from home to feel at ease. PM2.5 dust detection: The environmental conditions in cities across China are now in a period with high levels of fog, and people are gradually beginning to experience the ‘pain of breathing’. Factors such as smoking indoors, the fumes generated during cooking, and incompletely burned gas all contribute to an increase in the concentration of PM2.5 particles in the air, which can lead to various diseases. The impact is particularly severe on the elderly, children, infants, and those who already suffer from respiratory or cardiovascular diseases. The PM2.5 dust sensor counts the number of particles in the air by utilizing the scattering of infrared light by dust particles; it is capable of detecting particles with a diameter of 1 um or more. It features a built-in heater that enables automatic air intake, thereby reducing measurement errors. Additionally, it is compact in size and easy to install and use. Air purifiers are also electrical appliances commonly used indoors that contain gas sensors. Gas sensors integrated into central devices such as security cameras or smart speakers can even remotely monitor the home environment in a room in real time, control ventilation from a distance, and ensure that the indoor air remains clean and fresh whenever people enter the room. Air safety monitoring in high-end smart cars: According to surveys, 93.6% of new cars have indoor air pollution levels that far exceed acceptable limits. The sources of air pollution in vehicles come mainly from the vehicle itself and the materials used for decoration; toxic substances such as formaldehyde, xylene, and benzene pose the most serious risks, as they can lead to cancer. Another type of harmful gas found in vehicles that is often mentioned in the news is carbon monoxide, known as the \"silent killer.\" Its main sources are car engines and vehicle exhausts, as well as the use of the air conditioning system while the car is parked. When this colorless and odorless poison accumulates inside a vehicle, those inside can die from poisoning without even realizing it. By using appropriate gas sensors, it is possible to monitor volatile organic compounds such as formaldehyde, xylene, and benzene inside the vehicle, as well as the carbon monoxide concentration there; this serves as a safety alert to remind drivers to take effective measures to prevent tragedies from occurring. Furthermore, in application scenarios such as smart buildings, smart venues, smart schools, smart parking lots, smart public toilets, and smart farms, the appropriate gas sensors are installed based on the requirements of each scenario. By utilizing long-term monitoring data, appropriate control measures can be taken to improve the quality of indoor air and the overall environmental conditions. Gas sensors can also play a significant role in areas such as non-invasive exhaled gas detection, global greenhouse gas monitoring networks, and the inspection of natural gas production processes. Machine olfaction on the rise: Gas sensors represent a $920 million market opportunity. Currently, in the domestic market, there is an increasing demand for environmental monitoring services. With the continuous strengthening of ecological management measures, air monitoring will enjoy broader market prospects. At the same time, **guidance is being strengthened at a macro level for the air monitoring equipment industry, in order to fully leverage domestic advantages, enhance the competitiveness of domestically produced monitoring equipment, and promote healthy development of the industry. In the global market, as the world warms up, the frequency of extreme weather events is changing, showing an increasing trend. As a result, the demand for gas sensors is also on the rise; it is estimated that by 2021, the global market size for gas sensors will reach 920 million dollars. With the rise of the end-user consumer market, demand for gas sensors in the global consumer sector continues to grow at a rapid pace. In 2015, the global shipment volume of gas sensors for consumer use was around 1.3 million units; this figure rose sharply to 100 million units by 2018. It is expected that demand will increase to 350 million units by 2020, presenting a new wave of development opportunities for the gas sensor industry. From a technical perspective, the future of gas sensors looks promising. On the one hand, the development of intelligent technologies is driving gas sensors toward intelligence. Gas sensors will develop by making full use of a combination of technologies from various fields, including micromechanics and microelectronics, computer technology, signal processing technology, sensing technology, fault diagnosis technology, and intelligent technology. The development of fully automatic digital intelligent gas sensors capable of monitoring multiple gases simultaneously will be one of the future trends. On the other hand, research on new materials will lead to innovations in gas sensors. New material development technologies such as nanomaterials, graphene, and thin-film technology have been successfully applied to gas sensors, **improving their performance. For example, by adding boron atoms to graphene, gas sensors have been developed that possess extremely high sensitivity; they can detect harmful gases at very low concentrations in the air and issue an alarm before people are even aware of their presence. Conclusion: The future belongs to the world of machines, but currently everyone’s attention is focused on speech recognition, machine vision, facial recognition, and machine language, while another very important sense is being overlooked: smell—the ability of machines to detect molecules in their environment. In fact, whether it is to monitor the quality of the air we breathe on a daily basis, to conduct inspections of hazardous materials, or to detect toxic gases, machines need to have the ability to sense environmental molecules in order to identify any harmful gas molecules present in the environment. Paying attention to and developing gas sensors is not only a market opportunity but also a wise move to ensure survival.