A hydrogen cyanide (HCN) gas detector is a critical safety device that accurately senses and measures the concentration of HCN in the air. These detectors are essential for personal protection in hazardous gas environments where exposure to HCN may occur. Hydrogen cyanide is widely used in various industrial processes, including chemical manufacturing, fumigation, mining, electroplating, and the production of synthetic plastics. Additionally, HCN can be released during reactions between cyanide and acid or during combustion. By continuously monitoring the air and providing real-time HCN concentration measurements, these gas detectors help protect workers and ensure their safety in industries where hydrogen cyanide is present.
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Best Hydrogen Cyanide Gas Detector?
There are many hydrogen cyanide gas detectors on the market. The reputable brands include the following:
- Forensics Detectors Hydrogen Cyanide Detector
- RC Systems Hydrogen Cyanide Detector
- Draeger HCN Detector
- Honeywell HCN Gas Detector
What Is a Hydrogen Cyanide Gas Detector?
A hydrogen cyanide (HCN) gas detector is an instrument used to detect the concentration of hydrogen cyanide in the air. These devices (specifically the Forensics Detectors FD-90A-HCN) have a long-life battery, large screen that displays the HCN concentration, and a belt clip to connect to clothing. In order to protect users, these gas detectors also have LED, vibration, and buzzer alarms.
Hydrogen cyanide gas detectors are also known as HCN monitors, hydrogen cyanide sniffers, hydrogen cyanide analyzers, and HCN gas testers. These names all refer to the same device, an HCN gas detector.
What Does a Hydrogen Cyanide Meter Detect?
A hydrogen cyanide detector senses HCN gas and displays the levels in parts per million (ppm).
The growth of hydrogen cyanide detectors has increased due to its use as a fumigant in response to the need to replace methyl bromide. Hydrogen cyanide is used against scale insects on citrus trees and other pests on greenhouse plants.
What Is Hydrogen Cyanide Gas?
Hydrogen cyanide has the chemical symbol HCN. It is a very useful yet dangerous gas, hence the need to monitor and check air concentrations.
Is Hydrogen Cyanide Toxic?
Yes it is.
Hydrogen cyanide is a systemic chemical asphyxiant, interfering with oxygen usage in the body. When exposed to hydrogen cyanide gas, the brain, heart, and lungs will be affected and can become rapidly fatal. Avoiding hydrogen cyanide gas exposure is essential to protect your family and coworkers.
HCN fumes are also dangerous to animals. Levels of hydrogen cyanide as low as 0.2 ppm were found to be toxic to fish.
In 2017, an electrical fire filled up a three-story house with toxic smoke. In just ten minutes, a pair of cats died from hydrogen cyanide poisoning. Luckily, a couple of other cats and the other occupants made it out unscathed.
What Should I Do If I've Been Exposed Hydrogen Cyanide Gas?
If you suspect that you have been exposed to hydrogen cyanide, it is important to evacuate to an outdoor environment with no traces of HCN exposure. Seek medical attention immediately. Medical professionals can help manage symptoms such as reduced respiratory or heart function.
Preventing exposure is important for safety and can be achieved with an HCN gas detector.
Can I Smell Hydrogen Cyanide Gas?
Yes, most humans can smell hydrogen cyanide gas. It is described to have a bitter almond smell. The gas doesn't always give off an odor and even when it does, it cannot be detected by everyone.
The hydrogen cyanide odor threshold is around 0.6 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 HCN. Over time, the nose becomes desensitized to the odor - this phenomena is called olfactory fatigue.
What Are the Different Types of Hydrogen Cyanide Gas Detectors?
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Hydrogen Cyanide Detector for Personal Protection |
The majority of hydrogen cyanide gas detectors are portable. These are small, battery-powered units with an HCN sensor that can be clipped onto your clothes for personal protection.  |
| Hydrogen Cyanide Gas Monitor for Stationary Fixed Wall |
Wall-mounted units provide continuous protection and warning of hydrogen cyanide gas leaks. These devices are perfect for indoor uses. If the levels pass the preset threshold (i.e., 10 ppm OSHA TWA), the unit will provide an LED and buzzer warning.  |
How Does a Hydrogen Cyanide Gas Sensor Work?
An hydrogen cyanide gas detector is composed of electronics and an HCN 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 HCN concentration reading. If the measurement exceeds the pre-set alarm value, the alarms are triggered.
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Sensor Technology |
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Hydrogen Cyanide (HCN) |
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 Hydrogen Cyanide Gas Levels?
Various government agencies have recommended 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): 4.7 ppm, 10-hour TWA 4.7 ppm, 10-minute ceiling |
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Occupational Safety and Health (OSHA) |
4.7 ppm average over 8 hours 4.7 ppm average over 15 minutes (Permissible Exposure Limit) |
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American Conference of Governmental Industrial Hygienists (ACGIH) |
4.7 ppm average over 8 hours |
What Is a Hydrogen Cyanide Gas Detector Used For?
Hydrogen cyanide gas is used in a variety of manufacturing and industrial processes, as listed below. Because HCN is toxic, it is important to monitor for employee and homeowner safety.
- HCN for fumigation: Hydrogen cyanide is used as an insecticide and fungicide. Stored grains facilities, ships, and other buildings can be fumigated with hydrogen cyanide gas to protect from pests. It is effective against a wide range of pests and has been used as a fumigant for over a century. Proper equipment and employee training is essential to protect human health.
- HCN for electroplating: Manufacturing activities such as electroplating, metal mining, metallurgy, and metal cleaning can be achieved with hydrogen cyanide.
- HCN for manufacturing: Hydrogen cyanide is used widely in the production of synthetic fabrics, plastics, paper, and dyes.
Can Hydrogen Cyanide Gas Contaminate Food or Water?
Yes, hydrogen cyanide can contaminate water and food through factory emissions. The EPA and other agencies have thresholds put into place to protect the public from HCN toxicity. This is why it is so important that facilities monitor their HCN output using a hydrogen cyanide detectors.
How Long Does a Hydrogen Cyanide Sensor Last?
Hydrogen cyanide detectors incorporate electrochemical sensors that last between 24 and 36 months.
How Do I Test My Hydrogen Cyanide Detector?
The best way to test your hydrogen cyanide gas detector is to expose it to a known gas source. Bump testing is a good practice to perform daily. Frequent testing is especially important in personal protection applications where safety is paramount.
What Is a Hydrogen Cyanide Detector Bump Test?
- Bump testing is a procedure where the user exposes the HCN detector to a “blast” gas. The gas triggers a bump to the detector 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.
- Hydrogen cyanide bump test gas can be found here.
What Is Hydrogen Cyanide Detector Gas Calibration?
Hydrogen cyanide 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 HCN 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 HCN 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 HCN 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 Hydrogen Cyanide Gas Sensor?
- Store your HCN gas detector at a normal room temperature.
- Store it away from electromagnetic interference sources such as phones.
- Store it in a clean environment.
- Store away from any exhaust gas, concentrated vapors, and harsh chemicals.
- Clean the detector with a damp cloth.
- Store it in a stable place where there are no vibrations occur.
How Do I Properly Use an HCN Gas Detector?
When operating a HCN gas detector, there are some important tips to consider.
- Read your product manual, or watch any support videos.
- Turn ON the HCN gas monitor in the fresh air.
- Ensure the HCN 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.
Is Hydrogen Cyanide Gas Explosive?
Yes it is.
Hydrogen cyanide is flammable at concentrations above 5.6% in air.
Therefore, HCN gas has a lower explosive limit (LEL) of 5.6% - this means it is too lean to burn.
The upper explosive limit (UEL) of HCN is 40% - this means it is too rich to burn.
Can You Smell Hydrogen Cyanide?
Yes, hydrogen cyanide has a distinct bitter almond smell. However, 20-40% of people can't detect this odor due to genetic differences, making it especially dangerous.
Fatalities from Hydrogen Cyanide Exposure
Several fatal accidents involving hydrogen cyanide have been recorded:
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República Cromañón Nightclub Fire, Buenos Aires, Argentina (2004): This fire resulted in the deaths of 194 people, with at least 1,492 injured. Poisonous gases, including hydrogen cyanide, were released during the fire. The level of cyanide toxicity in the air was found to be extremely high, contributing significantly to the fatalities.
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Kiss Nightclub Fire, Santa Maria, Brazil (2013): Hundreds of young people were poisoned by cyanide gas released from the combustion of soundproofing foam made with polyurethane during a fire. This incident resulted in 245 confirmed fatalities.
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Use in Extermination Camps during the Holocaust: Zyklon B, a chemical containing hydrogen cyanide, was used by Nazi Germany in extermination camps during the Holocaust. It is estimated that about one million people were murdered using Zyklon B in gas chambers at camps like Auschwitz-Birkenau and Majdanek.
Final Words
Hydrogen cyanide (HCN) is a highly toxic gas used in various industries, such as fumigation, electroplating, and plastic manufacturing. Due to the severe health risks associated with HCN exposure, personal protection in hazardous gas environments is of utmost importance. HCN gas detectors play a critical role in ensuring worker safety by continuously monitoring the air and providing real-time measurements of HCN concentrations. These detectors can also identify gas leaks in fumigated areas and manufacturing facilities, allowing for swift action to prevent potentially catastrophic incidents. With HCN gas detectors being affordable, with units costing less than $399, there is no excuse for industries dealing with this toxic gas not to prioritize the safety of their workers. Proper use and maintenance of HCN gas detectors, along with comprehensive safety training, are crucial for maintaining a safe working environment and protecting the well-being of employees in industries where hydrogen cyanide is present.
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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