A sulfur dioxide (SO2) detector is a critical safety device that accurately measures the concentration of SO2 in the air. These detectors are essential for personal protection in hazardous gas environments where exposure to sulfur dioxide may occur. SO2 is widely used in various industrial applications, including chemical processes, wood pulp and paper bleaching, food processing, and waste treatment. Additionally, sulfur dioxide is generated during the combustion of coal and petroleum, as well as through volcanic activity. Recognized as a major pollutant, SO2 poses significant risks to both the workplace and the environment. By continuously monitoring the air and providing real-time SO2 concentration measurements, these gas detectors help protect workers and ensure their safety in industries where sulfur dioxide is present, while also contributing to the mitigation of environmental hazards.
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Best Sulfur Dioxide Detector?
There are many sulfur dioxide gas detectors on the market. The reputable brands include the following:
- Forensics Detectors Sulfur Dioxide Detector
- MSA Sulfur Dioxide Monitor
- Smart Sensor SO2 Detector
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Industrial Scientific Tango SO2 Detector
What Is a Sulfur Dioxide Detector?
A sulfur dioxide (SO2) gas detector is an instrument used to detect the concentration of sulfur dioxide in the air. These devices (specifically the Forensics Detectors FD-90A-SO2) have a long-life battery, large screen that displays the SO2 concentration, and a belt clip to connect to clothing. In order to protect users, these gas detectors also have LED, vibration, and buzzer alarms.
Sulfur dioxide gas detectors are also known as SO2 monitors, SO2 meters, sulfur dioxide sniffers, sulfur dioxide analyzers, and sulfur dioxide gas testers. These names all refer to the same device, a sulfur dioxide gas detector.
What Does a Sulfur Dioxide Meter Detect?
A sulfur dioxide detector senses sulfur dioxide (SO2) gas and displays the levels in parts per million (ppm).
What Is Sulfur Dioxide Gas?
Sulfur dioxide has the chemical symbol SO2. It is a very useful yet dangerous gas, hence the need to monitor and check air concentrations.
Who are the Largest Polluters of SO2 Gas?
The largest polluters of sulfur dioxide gas (SO2) are typically industrial facilities, particularly those that burn fossil fuels such as coal and oil. Power plants, oil refineries, and smelters are some of the biggest sources of SO2 emissions. In addition, ships and other marine vessels that burn high-sulfur fuels can be significant sources of SO2 pollution, particularly in port cities. Some industrial processes, such as the production of paper and pulp, can also release significant amounts of SO2 into the atmosphere. In general, any activity that involves the combustion of sulfur-containing fuels or materials can contribute to SO2 pollution.
Is Sulfur Dioxide Gas Toxic?
Yes it is.
When exposed to SO2, you may experience respiratory irritation, lung injury, eye irritation, coughing, and headaches. Those with preexisting lung diseases, such as asthma or bronchitis, will typically be more sensitive to sulfur dioxide.
Studies have shown that SO2 exposure can increase the likelihood of irregular heartbeats and even cardiac arrest.
Can I Smell Sulfur Dioxide Gas?
Yes, humans can smell sulfur dioxide gas.
It has been described as having a strong and pungent odor. It is commonly described as smelling like rotten eggs or burnt matches.
The sulfur dioxide odor threshold is between 0.1 ppm and 4.7 ppm. See here.
However, it is a bad idea to rely on your sense of smell to determine the "concentration" of an aromatic gas like SO2. Over time, the nose becomes desensitized to the odor - this phenomena is called olfactory fatigue.
What Are the Different Types of Sulfur Dioxide Gas Detectors?
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Sulfur Dioxide Detector for Personal Protection |
The majority of sulfur dioxide gas detectors are portable. These are small, battery-powered units with a sulfur dioxide sensor that can be clipped onto your clothes for personal protection.  |
| Sulfur Dioxide Gas Monitor for Stationary Fixed Wall |
Wall-mounted units provide continuous protection and warning of sulfur dioxide gas leaks. These devices are perfect for indoor uses, such as a petroleum refinery that generates SO2. If the levels pass the preset threshold (i.e., 5 ppm OSHA TWA), the unit will provide an LED and buzzer warning.  |
How Does a Sulfur Dioxide Gas Sensor Work?
A sulfur dioxide gas detector is composed of electronics and an SO2 sensor. The gas sensor converts the detected gas concentration to an electronic signal for analysis by the onboard microprocessor. After receiving the electrical signal, the processor displays the SO2 concentration reading. If the measurement exceeds the pre-set SO2 alarm value, the alarms are triggered.
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Sulfur Dioxide (SO2) |
Electrochemical Sensors The gas reacts with a working electrode, triggering an electrochemical redox reaction. The generated current is proportional to the detected gas level. |
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What Are Safe Sulfur Dioxide Gas Levels?
Various government agencies have recommended SO2 gas exposure limits, examples can be seen below:
Agency |
Recommendation / Requirement |
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National Institute for Occupational Safety and Health (NIOSH) |
NIOSH Recommended Exposure Limit (REL): 2 ppm, 10-hour TWA 5 ppm, 15-minute ceiling |
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Occupational Safety and Health (OSHA) |
2 ppm average over 8 hours 5 ppm average over 15 minutes (Permissible Exposure Limit) |
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American Conference of Governmental Industrial Hygienists (ACGIH) |
0.25 ppm average over 8 hours |
What Is a Sulfur Dioxide Gas Detector Used For?
Sulfur dioxide gas is used in a variety of manufacturing and industrial processes, as listed below. Because SO2 is toxic, it is important to monitor for employee safety.
- SO2 for chemical processes: SO2 is a necessary reagent to manufacture sulfuric acid. It can also be used as an intermediate, oxidizing/reducing agent, and for bleaching in many chemical processes.
- SO2 for paper manufacturing: Paper mills use sulfur dioxide to treat wood pulp. SO2 is used to wash wood pulp and help paper products maintain their white color after bleaching. This can result in elevated levels of hazardous vapors.
- SO2 for preserving food products: Due to its antimicrobial properties and ability to prevent oxidation, SO2 is used as a preservative for many dried fruits. It prevents rotting from bacteria in wine.
- SO2 generation during fuel combustion: Fuel sources, such as coal and petroleum, often contain sulfur compounds that produce SO2 when burned. Workers can be exposed to high levels of SO2 during combustion, leading to toxic gas exposure. Coal and oil combustion accounts for 75% of the total SO2 emissions.
I Live Next to an Active Volcano, Should I Have an SO2 Gas Meter to Check My Levels?
Yes you should.
When there is increased volcanic activity in Hawaii, we see the sales of SO2 meters increasing. We saw this in Hawaii in 2018 with the Kilauea eruptions.
Volcanos emit SO2 and these levels vary based on changes in vent locations, eruption character, and vigor. Sulfur dioxide also interacts with moisture to produce acidic rain.
Having a low cost SO2 gas detector when residing close to a volcano is an excellent idea to ensure safety.
How Do I Select a Sulfur Dioxide Detector?
To select the best sulfur dioxide gas detector, follow this simple guide:
- What do I need it for?
- Personal Protection?
- Continuous Room Monitoring?
- What is my budget and operating cost budget?
- Do I need advanced functions such as data-logging or Bluetooth?
- Do I need specific accreditations with the monitor such as ATEX or a NIST traceability calibration certificate?
- Do I require a belt clip for attaching the device to my clothes?
- Do I need after-sales support, USA headquarters, or fast calibration services?
How Long Does a Sulfur Dioxide Sensor Last For?
Sulfur dioxide detectors incorporate small electrochemical sensors that usually last between 24 and 36 months.
How Do I Test My Sulfur Dioxide Detector?
The best way to test your sulfur dioxide gas detector is to expose it to a known gas source. Generally referred to as bump testing, this is a good practice to perform daily. Frequent testing is especially important in personal protection applications where safety is paramount - more about bump testing in the next section.
What Is a Sulfur Dioxide Detector Bump Test?
- Bump testing is a procedure where the user exposes the detector to a small amount of “blast” target gas to ensure the detector operates and alarms as programmed.
- The function of this test is to verify proper operation and build user confidence, particularly in hazardous applications.
- It is recommended to bump test when first purchased, with subsequent testing every week. If using in LIFE-THREATENING and / or DANGEROUS applications, bump test daily.
- Sulfur dioxide bump test gas can be found here.
What Is Sulfur Dioxide Detector Gas Calibration?
Sulfur dioxide gas detector calibration is the technical task of adjusting the detector to a more accurate gas reading. Over time, the sensors on the device will degrade or produce drifting readings. We suggest calibrating your SO2 detector every 6 to 12 months, the typical time period for gas detectors.
Gas calibration is a technical task that requires certain key pieces of equipment. These include a calibration gas bottle, gas regulator, tubing, and calibration cap fitting. You need to communicate with the manufacturer to determine the recommended calibration gas concentrations and mixtures. For the Forensics Detectors SO2 gas monitors, we recommend the calibration gas here.
Be attentive and calibrate daily if:
- The user employs the device as an analytical tool where accuracy is paramount.
- The device is used in an extreme environment (temp and humidity extremes create sensor drift).
- The user is performing an imminently dangerous application.
- Bump testing fails. In this case, you must calibrate to make sure the sensors and monitor operate properly.
- The SO2 gas detector alarms in the fresh air. This could mean that the sensor has drifted past an alarm set-point.
Calibration and bump testing are mandatory because injury or death can occur if the device fails. Take it very seriously.
Also, it is prudent to have a calibration schedule that the owner or employees strictly follow. See gas calibration here.
How Do I Take Care of My Sulfur Dioxide Gas Sensor?
- Store your SO2 gas detector at a normal room temperature.
- Store it away from electromagnetic or magnetic sources, such as phones.
- Store it in a clean environment with no dust or particles.
- Store away from any exhaust gas, concentrated vapors, and harsh chemicals.
- Clean the casing of your detector with a damp cloth.
- Store it in a stable place where there are no vibrations or continuous shaking.
How Do I Properly Use an SO2 Gas Detector?
When operating an SO2 gas detector, there are some important tips to consider. After reading your product manual, be sure to keep these tips in mind:
- Turn ON the SO2 gas monitor in the fresh air.
- Ensure the SO2 gas monitor is within its calibration period.
- Ensure the monitor has been bump tested and validated as operational.
- Check the alarm set-points. Set your alarms as desired (some units may not have adjustable alarms).
- If performing analytical measurements, keep the unit stationary. Ensure humidity and temperature are also tracked and are as constant as possible.
Are there Other Names for Sulfur Dioxide (SO2) Gas?
Some of the common alternative names for SO2 include sulfurous anhydride, sulfur oxide, sulfuric oxide, and sulfenous anhydride. Additionally, SO2 is sometimes referred to as "acid rain gas" because it can contribute to the formation of acid rain when it reacts with other compounds in the atmosphere.
Can You Smell Sulfur Dioxide?
Yes, sulfur dioxide has a distinctive pungent, irritating odor similar to a struck match or burning sulfur. Most people can detect its strong smell at concentrations around 0.5 ppm.
Final Words
Sulfur dioxide (SO2) plays a significant role in modern life, being essential for numerous industrial processes and commonly generated during fuel combustion. However, the widespread presence of this toxic gas also necessitates robust safety measures. SO2 gas detectors are crucial for personal protection in hazardous gas environments, ensuring the well-being of workers in industries that involve sulfur dioxide. These detectors continuously monitor the air, providing real-time measurements of SO2 concentrations and alerting users when levels exceed safe thresholds. Moreover, SO2 gas leak detectors are indispensable tools for identifying and addressing sulfur dioxide leaks, helping to prevent potential health risks and environmental hazards. With SO2 gas detectors being affordable, costing less than $350 per unit, industries that deal with sulfur dioxide should prioritize the safety of their workers and the surrounding community by implementing these life-saving devices. The use of SO2 gas detectors not only protects individuals but also contributes to the mitigation of environmental pollution caused by sulfur dioxide emissions.
About The AuthorDr. Kos Galatsis ("Dr.Koz") is the President of FORENSICS DETECTORS, where the company operates from the scenic Palos Verdes Peninsula in Los Angeles, California. He is a subject matter expert on gas sensor technology, gas detectors, gas meters, and gas analyzers. He has been designing, building, manufacturing, and testing toxic gas detection systems for over 20 years. 
Every day is a blessing for Dr. Koz. He loves to help customers solve their unique problems. Dr. Koz also loves spending time with his wife and his three children going to the beach, grilling burgers, and enjoying the outdoors. Read more about Forensics Detectors here. Email: drkoz@forensicsdetectors.com
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