Best Gas Detector FAQ (latest in 2024)

Best Gas Detector FAQ (latest in 2024)

When it comes to ensuring safety in environments with potential gas hazards, investing in a reliable gas detector is crucial. Although purchasing a gas detector may not be a frequent occurrence and can be costly, it is essential to allocate sufficient time and effort to select the most appropriate device for your specific needs. Gas detectors play a critical role in protecting lives and should be treated with the utmost seriousness. To help you navigate the complex world of gas detectors, we will provide guidance and address the most common questions, enabling you to make an informed decision when choosing this life-saving equipment.



  • Gas Detectors are a critical part in safety protection.
  • Helps with Gas Leaks.
  • Helps with Toxic Gas Exposure.
  • Most gas detectors are simple to operate.
  • Gas Detectors save lives and prevent injury. Be ready to call 911 if your gas detector indicates a dangerous gas leak.
  • May take effort to determine the correct gas detector for you.
  • Gas detectors need some love when it comes to bump testing and calibration. 
  • Do not breath into the gas detector.
  • Do not expose a gas detector to vehicle exhaust gas.

➡️ Which Gas Detector Do I Need?

The first question you need to answer is "what gas am I trying to detect?" If you do not know, then you need to do more research to narrow down one or two specific gases that you need to detect.

Common gases to be detected include CO, CO2, NH3, O3, O2, EX LEL, CH4, and many other exotic gases such as Cl2, C2H4, VOC, H2, He, Ar, and more. 

➡️ What is Gas Detector Range?

Once you know the gas to be detected the next question is, "what gas range and resolution do I need?" For example, if you are trying to find a carbon monoxide leak in your heating system, then you need a CO detector able to detect a few ppm, so a 0-1000ppm with 1ppm resolution CO gas meter will be required. If you do not know the concentration, you may need to do more research. Again if you are usure just email Dr. Koz.

➡️ What "type" of Gas Detector?

Once you have determined the gas to be detected and gas detection range, you now need to determine what type of gas detector you need. This may be self evident. The most popular categories of gas detectors are:

Portable Handheld Gas Detectors
These are usually small gas detectors made for mobility, personal protection, travel and exposure safety. Sometimes they are termed diffusive mode gas detectors, diffusion type, because they do not have a pump. That means the natural diffusion of gas molecule movement makes its way to the sensor from the surrounding environment. Examples would be our FD-90A, FD-103, and 4 gas detectors (confined spaces). These are the most common gas detectors.
Gas Detectors with Pumps and Probes
These are also portable gas detectors and most often handheld with an internal battery. The difference is that these units have an internal pump (sometimes external) to draw air into the unit and onto the sensor. Sometimes also called pump type, pumped type, forced air type, or pumping type, referring to the air being moved to the sensor via a pump. Sampling and pumping air to the sensor is advantageous as it increases detection speed and allows you to pinpoint specific locations to sample the gas. Most often achieved with a probe. These units are predominantly used for for leak detection, gas inspection, air quality assessment, R&D and gas assessments. Product examples would be our headspace analyzers FD-600 and FD-311 versions. These units are typically more expensive, since they have a build in pump and require a probe, making them physically larger and requiring more power.
Wall Mount Gas Monitors
Wall mount gas detectors are designed to be continuously ON and continuously sniff the indoor environment. The monitor will alarm once the gas threshold have been exceeded preset alarm levels. Sometimes they are battery powered or powered by 24VDC. Examples would be our FD-60 and FD-D001 models. 
Gas Leak Detectors with Gooseneck
These are generic combustible gas detectors that are great for finding natural gas leaks, sewer gas leaks, propane leaks or to test for combustibles in tanks and silos. The detectors do not have a pump and are diffusive. There are some models that actually do have a pump, and force the air into the gooseneck to create a pointed vacuum airstream onto the sensor element, often seen with heated diode refrigerant leak detectors. Basic gas leak detectors from us include the FD-90E and FD-91 versions.
Benchtop Gas Analyzers
These are larger units that typically are more expensive and have high gas detection performance specification. These units typically are also more accurate and have larger sensors and more electronics that provide the "higher performance" detection. Usually in the $1000s. Examples would be our FD-UVO3.

Can the Gas Detector be Used in Liquid?


Liquid gas testing otherwise known as dissolved gas in liquid is another skillset, and a specific sensor is required to detect gas in liquid such as that used for dissolved oxygen, dissolved ammonia, or dissolved ozone. We do not specialize nor sell liquid sensors as those products require special knowledge and expertise that we simply do not have. 

gas and liquid sensors

What Sensors Are in a 4 Gas Meter?

There are four sensors in a 4 gas monitor. Three of those sensors are electrochemical CO, H2S and O2. The EX LEL that is typically calibrated to methane is a catalytic type sensor able to detect most combustible gases. 4 gas meters are typically used for confined space applications.

How Long Do Gas Sensors Last?

Different sensors have different expected lifetimes. Identify which sensors you have and to determine their useful life. The lifetime should be within your user manual also. Over time, gas sensors degrade, they become less sensitive to the target gas which means they require more love, and more frequent calibrations. At a certain point, they degrade so much that they cannot be calibrated and must be discarded or replaced.

Electrochemical Sensors: Most of our gas detectors incorporate electrochemical gas sensors as the gas sensing element. These last between 2 to 3 years. Some electrochemical sensors, especially those used in our low level CO detectors, last 5 years or 7 years. Double check instructions to make sure you are 100% certain. Below is an image of a VOC electrochemical sensor Made in Switzerland by Membrapor.

Semiconducting Sensors and Heated Diodes: These are gas sensors based on solid state semiconducting metal oxide and last over 5 years. These sensors are found in our gas leak detectors. Below is an image of a combustibles MOS  sensor Made in Japan by Figaro.

Catalytic Bead Sensors: Catalytic Bead sensors lat between 2 to 3 years. These are used in our EX LEL gas detectors. They have 4 leads. Two leads to undertake sensing and two leads to heat the element. Below is an image of a EX LEL catalytic sensor Made in China by Winston.

Non Dispersive Infra Red NDIR and Laser Scattering: NDIR and laser scattering sensors last much longer than 5 years and most go strong up to the 10 year mark. These include our CO2 sensors and vape detectors. Below is an image of a dual CO2 NDIR sensor Made in China by Cubic.

What is Gas Detector Accuracy?

Accuracy is mostly a function of gas calibration, rather than a magic inherent gas detector performance metric. It amuses me (Dr. Koz) when customers make purchasing decisions based on accuracy and errors from a datasheet, rather than asking anything about calibration. Ok, so what does that mean?

It means that if the detector has been freshly calibrated, then that is the only way one can be assured of any objective gas detector accuracy. And if freshly calibrated, then it will be very accurate! For example, if you have just purchased an ozone detector and it reads 1.00ppm, then most likely it will be exactly 1.00ppm (with a calibration error of +/- 0.05ppm). Now, this is a fresh gas detector, freshly calibrated and turned on days after calibration. With time, all sensors degrade. Yes all gas sensors, gas detectors and analyzers degrade, this is fact of life. So the accuracy also degrades and over time instead of reading 1.00ppm, it may read 0.9ppm. This is why we recommend 6 month to 12 month calibration periods to ensure accuracy. 

Now, officially however, all gas detectors must report accuracy specifications which are typically presented as "<5% F.S." on the specification sheet (see below example of our FD-90A series). F.S. stands for FULL SCALE, which refers to the range of gas concentration that the detector can measure. However, some customers misunderstand this metric as a do or die "figure of merit" when in reality, good calibration is the upmost paramount factor for accuracy.

An example of F.S. is as follows. Let us assume you have a carbon monoxide (CO) analyzer with a range of 0 to 1000ppm and a reported accuracy <5% F.S. Then 5% of 1000ppm is 50ppm. This means that the worst case reading in terms of accuracy would be 50ppm under high temperature and humidity conditions. Again this is WORST CASE scenario. However, this does not mean that the detector will always read 50ppm at 0ppm gas concentration. It is important to test the gas under "normal room temperature conditions" to obtain the most accurate readings, which are defined as close to the conditions of calibration. These conditions are usually stated in the gas detector calibration certificate.

How Can my Gas Sensor Fail?

  • Gas Sensor Poisoning occurs when a high amount of gas is exposed to the gas sensor. This may occur when the amount of gas exposed to the sensor is unknown. When this occurs the sensor will exceed the designed maximum gas readout. If excessive, a tell tail sign is that the sensor will not come back to its zero baseline indicating the calibration of the unit has been compromised. In some cases, the sensor may be permanently damaged and may beed to be replaced. Hence the reason we advocate to bump test to a known gas concentration that is below the maximum range, yet higher than the alarm level in order to trigger and confirm gas detector operation.
  • Gas Sensor Leakage: Electrochemical gas sensors can corrode at the electrodes as they are made of an electrolyte solution. The packaging may be compromised and they may leak. Leakage of solution is common with oxygen electrochemical gas sensors.
  • Excessive Pressure or Vacuum: Electrochemical gas sensors are rated to only work at ambient pressure, 1 atmosphere. The sensors are sealed with a hydrophobic PTFE membrane to prevent fluid from flowing in and out, even if there are holes for gases to flow through. Leakage will occur if the pressure at the sensor inlet suddenly increases or decreases and will permanently damage the sensor. 

What is Bump Testing?

Bump testing is a procedure where the user exposes the detector to a small amount of gas from a Bump Test Source in order to obtain a a response from the gas detector and confirm alarm functionality. It serves to confirm gas detector operation and builds user confidence.

It is recommended to bump test when you first obtain your gas detector, followed by weekly tests. This is especially important in LIFE THREATENING and / or DANGEROUS applications to verify detector operation where daily bump testing is recommended (being used as a PPE device). It is also handy to be aware of OSHA requirements regarding bump testing and calibration, see here. Of note also, be aware of the International Safety Equipment Association (ISEA) requirements regarding bump testing and calibration, see here.

What is Gas Detector Calibration?

Gas detector calibration is a technical procedure performed every 6 to 12 months to ensure your device is functioning accurately. Over time, gas detectors and their respective sensors degrade at different speeds. The only way to ensure accurate and repeatable measurements is through gas calibration. The more often you calibrate the more accurate you can be assured your unit will operate. 

gas detector calibration

There are two options when it comes to gas detector calibration.

Why are Gas Detectors Expensive?

Gas detectors can be costly due to the fact that they are a niche specialty product with a relatively low volume of sales. The primary expenses involved in the manufacturing of gas detectors are the gas sensor and labor costs. Gas sensors themselves can be expensive. When it comes to repairing or replacing a gas detector, the cost can sometimes be prohibitively high if USA labor is involved. This is particularly true for tasks such as gas calibration, which can be quite expensive due to the high cost of gas bottles and labor in the USA, compared to the lower costs of labor involved in manufacturing these products in China.

What Shall I do when I Smell Gas?

If it appears that there may be a gas leak in your home, it is recommended that you contact your gas company immediately to arrange for a FREE test. If it is safe to do so, you may also want to consider opening doors or windows to improve ventilation. Many gas companies offer free inspections to their customers, and they may use Gas Leak Detectors to scan gas lines, connections, and appliances in order to locate the source of the leak.

Can I Replace my Gas Sensor?

Yes you can. However, please consider the economics. Some detectors such as our FD-90A-H2S gas detector is sold for less than $99. These are mass manufactured and hence the price is low. A H2S sensor costs $85. So in this case, it does not make economic sense to replace the sensor since calibration costs another $75. 

When the sensor price is well below half the price of a new detector such as a NO2 detector, where the NO2 sensor costs $165 a sensor replacement would be viable. In this case, it would be worth replacing the sensor, also considering the calibration cost, one would still be financially on top, rather than purchasing a new NO2 gas detector.

No you cannot. Some Gas Sensors cannot be replaced as the Gas Detector has been designed such that the sensor cannot be changed. This is the case for example of our FD-TRAVEL001, FD-J001, and others.

    Does the Gas Detector tell me which Gas is Being Detected?

    No it does not. There is no detector that is able to analyze and identify the gases that it detects. This is a fallacy and such capability does not exist. 

    Which Gas Detector is Best for Indoor Air Quality?

    The most common gas detectors for indoor air quality assessment includes:

    1. Carbon Dioxide (CO2)
    2. Carbon monoxide (CO)
    3. Particulate and dust (PM2.5)
    4. Combustibles (methane, propane)
    5. Volatile Organic Compounds (VOC)

    The most frequently encountered air quality issues in homes are related to these gases. It is recommended that you consult the exposure recommendations from reputable organizations such as WHO, OSHA, NIOSH, and ACGIH to help address these concerns. If you suspect that the air quality problems in your home are caused by more uncommon or exotic gases, it may be beneficial to obtain an air quality assessment from a professional environmental company that specializes in air quality testing.

    How to Detect Sewer Smell?

    For sewer gas leaks, we recommend our Sewer Gas Leak Detector. Sewer gas leak detectors can be useful in the identification of combustible gases and many such detectors have the capabilities to identify several gases common to sewer gas leaks that includes ammonia, methane and hydrogen sulfide. They are particularly helpful for plumbers, inspectors, water works, HVAC, contractors and maintenance engineers.

    Can I Breathe on my Gas Detector?


    If you happen to exhale onto a gas detector, you may observe a reaction from the device. We frequently receive calls from customers who are perplexed by this occurrence. The reason for this is that the sensor is being exposed to high humidity and temperature, which can cause it to read erroneous data. Additionally, in some cases, the high concentration of CO2 in exhaled breath can also affect the gas sensor. While breathing on the sensor will not damage it, it will produce inaccurate readings due to the excessive humidity in our breath, which exceeds the acceptable limits of the gas detector. Therefore, it is recommended that you avoid breathing on the gas sensor to prevent receiving false data.

    Can you Test a Carbon Monoxide Detector with Car Exhaust?


    Using vehicle exhaust gas as a source of gas for testing your gas detector is not recommended for several reasons. Firstly, the concentration of carbon monoxide and other gases in exhaust gas is not constant and can vary depending on several factors such as engine tuning, engine temperature, exhaust volume, engine load, catalyst age, and more. This makes it an unreliable source for testing your gas detector's functionality.

    Secondly, exhaust gas contains a large amount of humidity and is expelled at high temperatures, which can damage the gas sensor and give a false reading. The high temperature and humidity can also cause moisture to condense on the sensor, further affecting its accuracy.

    Lastly, exhaust gas contains acidic gas components such as NO2, which can cancel out the real CO sensor output. To use exhaust gas as a source of gas for testing, special filters are needed to remove humidity, treat acidic gases, and condition the exhaust stream before exposing it to the gas sensor. 

    The best way is to use Carbon Monoxide Bump Gas or Calibration Gas. If you dont have that, then we recommend video below.

      How Can I Check my CO Detector?

      The best way is to use Carbon Monoxide Bump Gas or Calibration Gas. If you dont have that, then we recommend video below.

      Can I take my Gas Detector on the Plane?

      Yes. All gas detectors we sell can be taken on a plane and OK with the FAA.

      Do I Need a Pump for my Gas Detector?

      It depends on your application. For personal protection, passive detection such as personal exposure, you do not and difussive mode detectors are just fine. For inspection, assessment and point sampling, then you do need pumping. This is explained in the video below.

      I Smell Gas but my Gas Detector Shows Zero?

      There are two reasons this occurs.

      • Your nose is too sensitive and better than the gas detector. The human nose is highly sensitive to smelly gases such as Hydrogen Sulfide, Ozone, Chlorine, and many others, even at sub-ppm levels, which are less than 0.1ppm. This is due to the fact that the nose has been evolving for hundreds of thousands of years to become extremely adept at detecting odors. As a result, it can sometimes be difficult for a $400 electronic gas detector to compete with the nose in terms of sensitivity.The human nose has a remarkably low odor threshold and is capable of detecting certain gases at levels as low as 1 part per billion (ppb). This is an incredibly small concentration, but the nose is able to pick it up thanks to its intricate design and the vast network of olfactory receptors that it contains.
      • The gas detector you purchased is not sensitive enough. This often happens when customer purchase the "cheaper" version. For higher sensitivity, you may need the 0.01ppm instead of the 1ppm. For example, often we see customer purchasing our 0.1ppm resolution ozone meter, when they should be purchasing the 0.01ppm resolution ozone meter. 10 times the sensitivity but double the price. And for those that are we cannot magically by the press of a button make a gas detector magically become more sensitive - the sensitivity is set by the gas sensor internal to the gas detector.

      Gas Detectors for Outdoor Air Quality?

      We often receive calls regarding testing outdoor polluted air. Outdoor air is ever expansive and pollutants typically dilute down past ppm concentrations and down to ppb concentrations. Typical for CO, Ozone, NOx and other pollutants. Detecting pollutants in the outdoor environment requires highly sensitive analyzers that we do not sell. As a first step, it is best to consider checking your local air quality station (enter ZIP then click on Monitor Near Me).

      Gas Detectors for Freeway Traffic Pollution?

      To determine if your indoor air quality has been polluted by adjacent traffic, typically the following gas detectors are employed for assessment:

      Gas Detectors for Volcanic Pollution?

      To determine if your indoor air quality has been polluted by volcanic pollution, the following gas detectors are employed for assessment:

      Gas Detectors for Kids Vaping?

      Parents often purchase our Vape Detector to monitor child vaping activity.

      Gas Detectors for Scuba Diving?

      To determine if your tank gas levels, the following gas detectors are employed for assessment:

      How do I Store My Gas Detector?

      The optimal storage conditions for gas detectors are at a temperature between 50F to 72F  and a relative humidity between 40 - 60%. This means that it should not be subjected to excessively cold or hot temperatures, and should be kept in an environment that is not too dry or too wet. Additionally, it should be stored away from any chemicals, avoid volatiles and particularly acids or bases, and in a clean dust free environment. 

      What Maintenance Schedule Shall I have for my Gas Detector?

      To ensure safety we recommend the following schedule for your gas detector. This is a generic framework. For those working in dangerous confined spaces, we recommend bump testing daily. For R&D where accuracy is upmost important, we recommend calibration daily. In general however, the tests and schedules that are important to ensure, operation, accurate and safety include:

      1. Bump Testing (weekly to monthly, sometimes even daily)
      2. Calibration Schedule (every 6 or 12 months)
      3. Maintenance Schedule (monthly)
      4. Replacement Schedule (2-3 year sensor replacement schedule, or as recommended)

      Which Gas Detectors are Used By Professional Home Inspectors?

      Home inspectors usually purchase:

      • Carbon Monoxide Analyzer: Inspecting CO from vents, cracked heater exchanges, leaking appliances and exhausts, testing for backdrafting.
      • Gas Leak Detector: Used to detect leaks of natural gas, propane and find sewer gas leaks.

      How do I Use my Gas Detector?

      Using a gas detector is typically a simple process. To begin, turn the detector on and allow it to start detecting. While some gas detectors may require additional steps, such as warm-up or stabilization time, most operate in a straightforward manner.

      It is important to note that certain gas detectors may require bump testing before use, particularly if they are being used as personal protection equipment. This involves testing the detector's response to the target gas to ensure that it is functioning properly.

      Additionally, it is important to follow best practices when it comes to bump testing and gas detector calibration to ensure accurate readings and reliable performance. Regular maintenance and calibration of gas detectors will help to ensure that they are functioning optimally and providing accurate readings.

      For indoor air quality testing, most often it is a matter of simply turning ON the gas detector and reading the digital display on the screen to obtain a gas concentration reading. Below is a super sensitive 0.01ppm VOC handheld analyzer taking a indoor air reading.

      There are however specialized cased such as Combustion analysis. In the case, a combustion analyzer is used in a certain way to obtain reliable combustion gas measurments.
      Below we have a oil and gas employee wearing a H2S monitor for personal protection to protect and alarm when the H2S level are high.

      What are the Gas Detector Measuring Units (ppm, ppb, %vol)?

      The concentration scale for any gas is typically measured in %vol or ppm (parts per million). This represents the percentage of the air volume occupied by the target gas volume. While other measures based on weight and mols exist, gas detection primarily relies on volumetric readings.

      The ppm scale has a direct conversion from %vol, where 10,000ppm is equivalent to 1% volume. These values are interchangeable. Once ppm values reach the thousands, it is common practice to use %vol instead. For example, it is simpler to express 1.1 %vol instead of 11,000 ppm.

      Sometimes ppb is used for very low concentrations. Conversion between ppm and ppb is as follows:

      1ppm = 1000ppb

      0.001ppm = 1ppb

      What Area does your Wall Mount Gas Detector Cover?

      Wall Mount Gas Monitors have no specific coverage area. Wall mount gas detectors detect gas molecules with a gas sensor. The sensor detects gas molecules that are directly adjacent to the physical sensor. The efficacy of the wall mount detector being representative and or correlated (gas concentration) to a larger area, is strongly dependent on the indoor physical layout, ventilation and any potential gas sources, obstructions or special exhaust considerations. Lets take some examples:

      Example 1: Standard Indoor Room with normal ventilation (>1 ACH).
      1x unit per 500 sq ft.

      Example 2: Warehouse industrial with normal ventilation (>4 ACH). 
      1x unit per 4000 sq ft. No obstructions. Other arrangement, like a wall is (2000 sq ft) or a corner setup is (1000 sq ft). See image below.

      Example 3: Active manufacturing line in an open floor plan space with gas (toxic or oxygen displacing) and potential leak sources. Coverage as close to potential gas leak failure locations.

      At what height shall I mount my Gas Detector?

      This depends on the gas detector and the relative gas density in air.

       Lighter than air
      Location: On or near the ceiling
      Hydrogen (H2)
      Methane (CH4)

      Breathing Zone

      Location: 4-6 feet above the floor

      Acetylene (C2H2), Ammonia (NH3) ppm, Carbon Dioxide (CO2) ppm, Carbon Monoxide (CO), Chlorine (Cl2), Ethylene (C2H4), Formaldehyde (CH2O), Fluorine (F2), Hydrogen Chloride (HCl), Hydrogen Cyanide (HCN), Hydrogen Fluoride (HF), Hydrogen Sulfide (H2S), Methanol (CH4O), Oxygen (O2), Ozone (O3), Nitric Oxide (NO), Nitrogen Dioxide (NO2), Phosphine (PH3), Silane (SiH4), Sulphur Dioxide (SO2), TVOC (target gas dependant)
      Near The Floor 
      Location: 6 inches above floor
      Alcohol, Benzene (C6H6), Carbon Dioxide (CO2) %Vol., Diesel Fuel, Ethanol (C2H6O), Gasoline, Hexane (C6H14), Isobutane (i-C4H10), Isobutylene (C4H8), Jet Fuel, Propane (C3H8), Pentane (C5H12), Propylene (C3H6), Refrigerants, Toluene (C7H8), Xylene (C8H10)

      What Is the Difference Between ppm and %LEL?

      Each combustible gas possesses a distinct lower explosive level (LEL) in air, which corresponds to its explosive limit. For instance, methane ignites in air when its concentration reaches 5% volume (equivalent to 50,000 ppm), which is referred to as the 100% Lower Explosive Limit. In essence, a gas's 100% LEL corresponds to the volume at which it can explode in the presence of an ignition source. Propane's 100% LEL is 2.1% volume, while hydrogen's is 4.0% volume. Therefore, the %LEL scale is primarily based on a gas's flammability or explosiveness, which differs from gas to gas.

      For instance, if a 4-gas detector reads 5% LEL, and it has been calibrated to methane, the reading equates to 0.25% volume or 2500 ppm. The explosiveness of methane gas is illustrated in the graph below.

      LEL diagram explosives 

      Final Words

      When it comes to ensuring safety in environments with potential gas hazards, investing in a reliable gas detector is paramount. Gas detectors play a critical role in protecting lives by continuously monitoring the atmosphere and alerting users to the presence of dangerous gases. Although purchasing a gas detector may not be a frequent occurrence and can be costly, it is essential to allocate sufficient time and effort to select the most appropriate device for your specific needs. To help you navigate the complex world of gas detectors, we will provide guidance and address the most common questions, enabling you to make an informed decision when choosing this life-saving equipment. Remember, gas detectors are not mere accessories but essential tools that require the utmost attention and seriousness.

      About the Author

      Dr. 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.

      gas detector expert

      Every day is a blessing for Dr. Koz. He loves to help customers solve their unique problems. He loves gas sensors and electronic measurement equipment such as digital oscilloscopes. 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.

      Phone: +1 424-341-3886