Fixed gas detectors are used to protect a facility in a single area and act as an early warning indicator of high gas levels or leaks.

These detectors are designed to alert workers of the potential danger of poisoning by toxic gas exposure, asphyxiation due to lack of oxygen, or explosion caused by combustible gases.

What is a fixed gas detector?

A fixed gas detector is a safeguarding system that constantly monitors a location due to the excess levels of gases. 

Unlike portable detectors, fixed detection devices make it possible to secure an entire area 24 hours a day.

They can also be connected to a detection system, which displays the gas concentration in numerical value, and then triggers the servo-controls in the event of an abnormal value.

Is a fixed gas detection system necessary?

Yes, a Fixed gas detection system is necessary as it is often required to protect facilities by the insurance companies that underwrite them and even by some standard electric codes.

It can alert potential danger before it occurs

Fixed detectors are used to detect an abnormal or dangerous presence of gas in a specific area and to warn the user in the event of potential hazards.

Equipped with sensors (called cells), they can measure the concentration of one or more types of gas, depending on the model. 

It will protect your facilities 24/7

Unlike portable detectors, fixed detection devices make it possible to secure an entire area 24 hours a day.

They can also be connected to a detection system, which displays the gas concentration in numerical value, and then triggers the servo-controls in the event of an abnormal value.

It can be connected with other security systems

Fixed gas detectors can easily be connected with other security systems like fire suppression systems, smoke detection systems, etc, to one control panel and help to simplify the control of your facility.

It is required by law

OSHA, NIOSH, NFPA, and other government agencies will want you to have some kind of a fixed gas detection system in certain facilities.

What are the Components of a Fixed Gas Detection System?

A fixed gas detection system consists of 3 parts: the sensor, transmitter, and controller.

The sensor

The sensor is the actual device that senses the gas. Many sensors, such as catalytic beads, infrared, and electrochemical, are used in gas detection.

Sensors typically last 2 to 4 years but can last longer or shorter depending on the application’s nature.

Solid-state and infrared sensors typically last much longer, and it is not uncommon for them to last 5 to 10 years or more.

Most fixed sensors can work as standalone units, but it is better to connect them to a transmitter and a controller if you want to integrate them with other systems.

The Transmitter

Most sensors require a transmitter to amplify the signal and convert the gas sensor signals into a standardized output, such as 4-20 mA, Modbus, and HART, for transmitting the signal to a controller.

The transmitter is usually close to the sensor, and zero and span adjustments must be done at the transmitter.

Most transmitters are operated from 24 VDC and utilize 2 or 3 wires. In general, even if a sensor can be used without a transmitter, the use of a transmitter is often preferred for distances over 300’ to 500’ to simplify the calibration effort.

In general, even if a sensor can be used without a transmitter, a transmitter is often preferred for distances of 300’ to 500’ to simplify the calibration effort.

The Controller

The controller is the device that receives and interprets the signals from the sensors and sensors/transmitters.

The controller typically provides a readout of the gas concentration, audible and visual alarms for dangerous gas levels, and general alarm relays for activating an external alarm or other action.

In some applications, it is preferred to send the transmitter signal (such as 4-20 mA) directly into a

PLC (Programmable Logic Controller) or other similar control devices. In this case, the PLC activates the alarm conditions and relays, and a “Gas Detection” controller is not necessary.

What is the best mounting height for fixed gas detectors?

This is one of the questions I get most of the time. In my experience, the mounting height at which a fixed sensor should be mounted depends on the density of the gas it monitors relative to the air.

Heavier than air

Gases that are heavier than air will tend to sink to the floor and concentrate there; my recommendation for the sensors that detect these types of gases is to mount them 1 to 3 feet from the floor.

Lighter than air

Gases like hydrogen and methane are lighter than air, which means the gases will rise and concentrate near the roof.

If you have a fixed gas detector to measure any gas that is lighter than air, you need to mount the sensors 1 to 3 feet from the ceiling.

Similar to air

Gases that have a relative density similar to air will be floating in the air near the breathing zone. Mount sensors in the breathing zone, which is 4–6 feet above the floor. 

If you do not know if the gas in question is heavier, lighter, or similar to air, you can google the relative density of that gas; if it is above 1, it means it is heavier than air; if it is less than 1, it means it is lighter than air; and if it is about 1, it means it is the same as air.

Tips for mounting fixed gas detectors

• Place sensors near the source of the gas, like piping or a compressor. 
• Mount sensors in areas with good air circulation, but not in areas with rapidly moving air. 
• Avoid mounting sensors near room entrances, fresh air intake vents, or vehicle/generator exhaust points. 
• Mount sensors upright on a vertical surface, like a wall, beam, or column. 
• Consider how accessible the sensor is for calibration and maintenance. 
• If you have a separate display from the sensor, mount it where it’s easy to read

FAQ: Fixed Gas Detection System

What is the difference between fixed and portable gas detectors?

Fixed Gas Detectors: Ideal for continuously monitoring specific areas or zones within facilities where gas hazards are present.

Portable Gas Detectors: Suitable for applications requiring mobility, such as confined space entry, leak detection, maintenance activities, or outdoor monitoring.

What are the two types of gas detection systems?

Gas detectors come packaged in two main form factors: portable devices and fixed gas detectors.

Final words

That is it. Those are the three main components of a fixed gas detection system. Thank you for reading.

A well-functioning gas detection system is an invaluable part of maintaining safety wherever gas is used.

Gas detection is critical to protecting human life and property in our homes or industrial complexes. In this article, I will discuss general gas detection.

What is gas detection?

Gas detection is the process of identifying hazardous gases in the air and alerting people to their presence. 

Gas detectors are used to ensure the safety of people and the environment by detecting combustible, flammable, and toxic gases, as well as low oxygen levels.

What is a gas detector?

A gas detector is a device that detects the presence of gases in an area, often as part of an industrial safety system.

A gas detector can alarm operators where the leak occurs, allowing them to leave.

Why gas detection is important?

Most commonly used gases, such as natural gas or Liquefied Petroleum Gas are invisible to the naked eye and highly explosive under the “right” circumstances.

To aid in detection, a strong-smelling odorant is added to the otherwise odorless gas. This allows the human nose to act as a gas detector.

Gas Detection is often necessary or desirable for several reasons. Here are four reasons why we need gas detection.

Safeguard life and property

A well-designed gas detection system will provide early warning of hazardous conditions, providing an opportunity for execution and notification for early re-entry for workers.

It will provide the time for intervention and correction and help trigger the facility, water mist, and fire suppression system.

Local fire safety codes and insurability

Most local fire codes and insurance companies will require you to have some gas and fire presentation systems in place to ensure the safety of workers.

Address real and perceived safety concerns

Most plants will emit some gas as a by-product of the production process. For example, the cells will produce hydrogen if you have a battery charging room.

As we know, hydrogen gas is toxic and flammable, so in this case, you will need a detector and controller to help with hydrogen monitoring in the facility.

Required by law

In most countries, some laws obligate manufacturers or certain industries to have a gas detection system in place.

Before installing any system, I recommend contacting a security firm in your local area so that they can assess what type of gas leaks can be found in your facility, and they will be able to recommend what system is suitable for you.

Also, you can call some of the gas monitoring instrument manufacturers and get their expert opinion.

Why you can not Rely on humans for Gas Detection

A properly installed and maintained gas detection system can detect leaks faster and more reliably than the human nose. The sooner you can act, the easier it is to limit the amount of leakage.

• Someone might not always be present when a leak happens. It can happen
  overnight.
• Gas can be heavier or lighter than the air in the room. This means that it
  will concentrate near the floor or the ceiling, where it may be out of reach
  of your nose.
• Whenever necessary, a gas detector can automatically activate a shut-off valve
  in the supply line and stop a leak.

Types of gas hazards

Explosive/combustible

These are gases that can combust if ignited in certain mixes of air, the most common combustible gases are Methane, Propane, Propane, Hydrogen, and Ethylene among others, these gases can be detected by the catalytic bead or Infrared sensors.

Toxic

These are gases that can be harmful to human health when we get exposed to them. Examples of these gases are Nitrogen Dioxide, Chlorine, Chlorine Dioxide, Carbon Monoxide etc.

Toxic gases can be detected by electrochemical sensors and paper tape.

Oxygen deficiency

When other gases increase in air, they will displace oxygen and cause Oxygen deficiency. If the Oxygen levels go below 19.5% volume, it can cause dizziness in people and at a lower rate, it might cause loss of memory, judgment, and eventually death.

Here are some gas detection basics

• 1ppm is one part in 1,000,000 parts. Generally, ppm (parts per million) is the lowest unit of measurement 10,000ppm = 1% by Volume
• LEL is the next unit of measurement. It is a percentage of a compound’s explosive %(vol) level.
• 100% LEL is the lowest concentration at which a flammable substance can produce a fire or explosion when ignited.
• UEL (Upper Explosive Limit) is the maximum concentration of gas in air that will burn.
• Each compound (gas) has a different LEL or the point at which the compound will burn or become explosive.
• Most flammable compounds become explosive at less than 5% (vol).
• Each gas has a different LEL and UEL.
• %Gas is the highest unit of measurement, the amount of pure gas.

nderstanding Explosion Limits

A leak with combustible gas can cause a fire or an explosion hazard in case we have an ignition source and the gas/air ratio in the surroundings is somewhere between the Lower Explosion Limit (LEL) and the Upper Explosive Limit (UEL).

If the gas concentration in the air is below the Lower Explosion Limit (LEL), ignition can’t happen.

Similarly, if the gas concentration is “rich”, meaning above the Upper Explosion Limit (UEL), ignition will not be possible unless the mixture is diluted with air.

Only in between the LEL and the UEL do we have a risk of ignition/explosion. Therefore, most gas detectors are calibrated to send an alarm signal a long time before we reach the critical Lower Explosion Limit.

Typically, the alarm level can be set at 20% of LEL. An early warning in due time before reaching the critical gas/air mixture (LEL) allows us to react and stop the leakage or leave the area.

How Do Gas Detection Sensors Work?

Most gas detectors detect oxygen deficiency, toxic gases, and combustible gases. Many technologies are used in the industry.

How does an Oxygen Sensor work?

The Oxygen Sensor is an electrochemical sensor. A fuel-based electrochemical sensor can detect any gas that can be oxidized or reduced electrochemically. 

The consumption of oxygen produces a current (µA), which is linearly proportional to the gas concentration in the air. 

Since the oxygen sensor is constantly exposed to oxygen, the normal life of the sensor is between 1-2years.

How does the combustible sensor work?

A combustible sensor consists of two coils of fine platinum wire, each embedded in a bead of alumina and connected electrically in a bridge circuit. 

One of the beads is impregnated with a special catalyst, which promotes oxidation, and the other is treated to inhibit oxidation. 

Current is passed through the coils so that they reach a temperature at which gas oxidation readily occurs at the catalyzed bead (about 500°C). 

This raises the temperature further, increasing the resistance of the platinum coil in the catalyzed bead, leading to an imbalance of the bridge. 

For most gases, this output change is linear up to and beyond 100% LEL, and response time is only a few seconds to detect alarm levels (typically 20% LEL).

How does the Toxic sensor work?

The Toxic Sensors are also electrochemical sensors operating with the same basic principles as the oxygen sensor.

Electrochemical sensors consume minute amounts of gas, and the absorption of gas and electric output is controlled by a “diffusion barrier.”

How do I know that a gas detector is required?

One good rule to go by is this: If there is a gas flange, coupling, or valve in the room, that room has a potential leak risk and should be fitted with one or more gas detectors.

In general, wherever 2 separate parts connect in a gas system, a gap can appear that lets out a small or large amount of gas.

Basements and rooms with open flames or limited ventilation require special attention!

Wherever the protection of people and properties is crucial, a well-designed gas detection system will increase safety levels and reduce the risk of hazards.

At what height I should mount my gas detector?

The type of gas you use determines the proper placement of your gas detector.

In the event of a gas leak, some gases float upwards while others sink to the floor.

This means that if your gas detector is wrongly placed, it may not be able to register the presence of gas before it has filled most of the room.

Therefore, if your gas is heavier than air (which is the case for LPG, propane, and butane), your gas detector
should be placed close to the floor (1 to 3 feet from the floor) and close to the ceiling (1 to 3 feet from the ceiling) if the gas is lighter than air (Natural gas/methane, hydrogen).

Ammonia is an example of a gas that is lighter than air, but because it absorbs moisture from the air, it eventually becomes heavier and sinks to the floor.

It could be recommended to place detectors both high and low when dealing with this gas, as ammonia is both toxic and explosive.

Propane and Butane are heavy gasses, and they will seek lower areas. Relative density > 1
Methane and Natural gas are light gasses and will stream upwards. Relative density < 1
(Relative density for air = 1)

An oxygen sensor should be mounted on the breathing zone.

What can cause a gas leak to happen?

When a gas leak occurs, it is often due to one of the following:

• Improper installation
• Lack of maintenance
• Worn-out equipment
• A faulty component
• Wrongful choice of sealant
• Human error

Portable gas detector or a fixed gas detector?

A personal or portable gas detector is the ideal safety tool for anyone who works in a hazardous environment.

Portable gas detectors let you check for gas leaks anywhere, and personal gas detectors simply clip onto your clothing and provide you with an instant alert if you find yourself in an area with critical gas concentration.

Fixed Gas Detectors are Ideal for continuously monitoring specific areas or zones within facilities where gas hazards are present.

Domestic or industrial gas detector?

For it to function optimally, the size and type of sensor in your gas detector must fit the space and conditions that it will be used in.
Domestic sensors are usually attractive in terms of price, but they are not designed for the rough conditions of industrial environments.
Industrial sensors are made for these spaces and will provide excellent safety anywhere. When in doubt, we always recommend an industrial-type sensor.

Gas sensors maintenance

Bump Check

A bump test is a functional test of the gas monitor, which ensures that the sensors will respond to their target gas and that the alarms will function.

This is performed by briefly exposing the sensors to their target gas. Bump testing should be performed before each day’s use.

Bump tests check for sensor and alarm functionality but do not measure sensor accuracy and do not make adjustments to the instrument in the way that calibration does.

Calibration

They must be calibrated regularly to keep sensors operating at peak efficiency and accuracy.

Calibration is part of the regular maintenance process, and it ensures that the monitor is reading the correct level of gas.

Portable detectors are exposed to various environments and must be calibrated more frequently than standing sensors.

Proper sensor maintenance is crucial. A contaminated sensor can misread gas levels, resulting in hazardous results.

Final words on gas detection

That is the gas detection overview. This article covered the definition of gas detection, its necessity, and how some of the most common sensors work. Thank you for reading.

Working in the fire industry for over five years has taught me the importance of understanding fire detection systems and how they can save lives and property.

Flame detectors play a crucial role in the early detection, response, and suppression of fires. Whether you’re protecting a home, office, or industrial facility, selecting the right flame detector can make all the difference.

What is a Flame Detector?

A flame detector is a sensor designed to detect the presence of fire by analyzing specific light spectrums or heat signatures. These devices are highly responsive and can initiate pre-programmed actions such as:

• Sounding fire alarms.
• Alerting central monitoring systems.
• Activating fire suppression systems.
• Deactivating gas or fuel lines.

The ability to quickly detect and respond to fires makes flame detectors indispensable in fire safety systems.

Types of Fire Detectors

Fire detectors come in various types, each using different technologies to detect flames. Understanding these options is key to choosing the right one for your needs.

Ultraviolet (UV) Flame Detectors

These detectors operate in the ultraviolet spectrum, identifying the UV radiation emitted by flames. UV flame detectors are highly sensitive and provide fast detection but can be affected by false alarms from UV light sources like welding arcs or sunlight.

Infrared (IR) Flame Detectors

Infrared flame detectors work within the infrared zone of the spectrum, detecting the heat signature of a flame.

They are reliable for indoor applications but may struggle with false positives from hot surfaces or sunlight.

UV/IR Flame Detectors

UV/IR detectors combine ultraviolet and infrared technologies to reduce false alarms while maintaining high sensitivity. They are a popular choice for environments with varying light conditions.

Multi-Spectrum Flame Detectors

These advanced detectors utilize multiple infrared sensors (commonly triple IR) to enhance accuracy and reliability.

They are designed for challenging environments where other detectors may fail, such as oil refineries or chemical plants.

Flame Imaging Detectors

Flame imaging detectors capture visual images of a fire and analyze them to determine the fire type and size. These are often used in specialized applications requiring detailed fire analysis.

How to Select the Right Flame Detector

Choosing the right flame detector depends on several factors. From my experience, these are the top three considerations:

Type of Fire You Need to Detect

Different flame detectors are designed to detect specific types of fires, such as:

• Hydrocarbon fires (e.g., gasoline, oil, or methane).
• Non-hydrocarbon fires (e.g., metals or hydrogen).

UV/IR or multi-spectrum detectors are ideal for hydrocarbon fires, while specialized detectors may be needed for unique fire types.

Environmental Conditions

Consider the environment where the detector will be installed:

Indoor vs. outdoor

UV flame detectors might struggle outdoors due to sunlight interference.

Hazardous areas

Multi-spectrum detectors are better suited for high-risk environments like chemical plants.

3. Required Response Time

In high-risk areas, response time can be critical. Technologies like UV/IR or multi-spectrum detectors offer faster response rates, making them suitable for environments with flammable materials.

Applications of Flame Detectors

Flame detectors are used across various industries, including:

• Oil and Gas: Monitoring flammable gas leaks and hydrocarbon fires.
• Chemical Plants: Detecting fire hazards in hazardous environments.
• Warehouses: Protecting stored goods from accidental fires.
• Power Plants: Ensuring safety in high-temperature and fuel-rich environments.

Key Tips for Maintenance

To ensure your flame detector remains effective, follow these maintenance tips:

1. Test detectors regularly to verify functionality.
2. Clean sensors to prevent dust or debris from obstructing detection.
3. Update software or firmware for advanced detectors like flame imaging systems.

FAQ: Flame Detectors

What is the difference between a flame detector and a smoke detector?

A flame detector identifies the presence of fire by analyzing light spectrums or heat signatures, whereas a smoke detector senses smoke particles in the air.

Flame detectors are faster at detecting fires in open areas, while smoke detectors are more suited for detecting smoldering fires indoors.

What type of flame detector is best for outdoor use?

UV/IR flame detectors are ideal for outdoor environments due to their ability to reduce false alarms caused by sunlight. Multi-spectrum detectors are another reliable option for challenging outdoor conditions.

How do I know which flame detector to choose for my application?

Consider three main factors: the type of fire you’re monitoring, the environmental conditions, and the desired response time.

For example, a UV/IR detector may work well in a warehouse, while a multi-spectrum detector is better for a chemical plant.

Are flame detectors suitable for detecting all types of fires?

Not all flame detectors can detect every type of fire. For instance, hydrocarbon fires are best detected by UV/IR or multi-spectrum detectors, while non-hydrocarbon fires (like hydrogen or metal fires) may require specialized technology.

Do flame detectors require regular maintenance?

Yes, regular maintenance is essential. Detectors should be tested and cleaned periodically to ensure accuracy and functionality. Advanced detectors, like flame imaging systems, may require software updates as well.

Can flame detectors prevent fires?

While flame detectors cannot prevent fires, they play a critical role in early detection, allowing for swift action to suppress the fire or evacuate the area.

What is the typical response time for a flame detector?

The response time varies depending on the technology used. UV flame detectors typically respond in milliseconds, while multi-spectrum detectors may take a slightly longer time depending on their configuration.

Are flame detectors affected by false alarms?

Some flame detectors, especially UV or IR types, may be prone to false alarms from sunlight, welding arcs, or other heat sources. UV/IR and multi-spectrum detectors are designed to minimize these issues.

Most of us spend most of our time at the office; therefore, maintaining adequate indoor air quality at the workplace is essential. In this article, I will share how carbon dioxide affects indoor air quality.

How does carbon dioxide affect indoor air quality?

There is a direct relationship between the amount of carbon dioxide in the environment and the air quality.

Carbon dioxide (CO₂) builds up in the atmosphere and causes Earth’s temperature to rise, much like a blanket traps heat. This extra trapped heat disrupts many of the interconnected systems in our environment.

In other words, if you want to improve indoor air quality, you need to make sure you control the amount of CO₂ in the environment.

What Carbon Dioxide does to the body

Exposure to carbon dioxide can produce various health effects. These include headaches, dizziness, restlessness, difficulty breathing, sweating, and asphyxia, among others.

Where does carbon dioxide come from?

Carbon dioxide is a natural component of air. The amount of carbon dioxide in a given air sample is between 250 and 400 ppm (parts per million).

Indoor concentrations can go higher than that because human beings inhale oxygen and exhale carbon dioxide; if the ventilation system is not well designed, it may cause an increase in the amount of carbon dioxide indoors.

How much carbon dioxide is too much?

The occupational safety standard for an industrial workplace requires a maximum level of 5000 ppm of carbon dioxide.

While the level of carbon dioxide below 5000 ppm is considered safe, some studies have shown that high levels of carbon dioxide are the direct result of drowsiness, lethargy, and reduced productivity.

What are the safe levels of carbon dioxide in rooms?

250-400 ppm

This is a normal background concentration in outdoor ambient air.

400-1000 ppm

This is the level of concentration typical of occupied indoor spaces with good air exchange. This is the value of concentration you should be aiming for.

1000-2000 ppm

When the level of carbon dioxide reaches this level, you should evacuate the building as soon as possible. At this point, most people will start to complain about drowsiness and poor air.

2000-5000 ppm

Stale and stuffy air, poor concentration, loss of attention, increased heart rate, and slight nausea may be present.

5000 ppm

This is the workplace exposure limit in most countries; the exposure limit is calculated as an 8-hour time-weighted average (TWA).

Above 40,000 ppm

At this point, the exposure may lead to serious oxygen deprivation, resulting in permanent brain damage, coma, and even death. You should make sure that it never gets to this point.

What to do?

My recommendation would be to monitor the air quality at your office; you can do this by having an air quality monitor at your office, and when you see the air quality start to drop, you can take the appropriate measures. I use the Airthings 2930 Wave Plus.

Conclusion

This is how carbon dioxide affects indoor air quality; my recommendation is to maintain it below 1000 ppm. You can do this by improving how the air circulates in your office.

Also, I recommend using an indoor air quality monitor to monitor the quality of air in your office; most of these monitors can be connected to the internet or an app so that they can warn you when the quality of air is getting worse.

Keep working hard and stay safe; thank you for reading.