A wireless gas sensor lets you measure the concentration of gases.
If they’re potentially explosive or toxic, wireless sensing lets you measure gases at a safe distance, perhaps in inaccessible places, providing real-time early warning… often with low set-up and operational costs.
A wireless gas sensor senses a specific target gas, for example, Carbon Dioxide, and transmits a signal that’s proportional to, or represents, its concentration. A receiver receives this signal and the measurement is processed and stored.
The processing may include the generation of an alarm if the gas
concentration exceeds a certain amount. Sometimes this amount, the
threshold, is programmable, but you need to take expert advice as the
selection of the appropriate threshold may be vitally important.
Always refer to hazardous substance fact sheets for exposure limits and other useful information put out by health departments.
Always get independent expert advice for any critical gas sensing installations.
Sensing potentially flammable or
explosive gases must only be carried out using intrinsically-safe
sensing systems - those that are, by design, incapable of igniting gases
under any circumstance, including malfunction.
Compressed gases are often stored in cylinders and used for many
different processes. But with this convenience comes risk… one that has
to be managed. Monitoring for leaks is an essential part of this
Always refer to health and safety guidelines. Government websites are a good source of information to learn more about specific gases and their hazards.
Because gases may be invisible and odorless, an electronic wireless gas sensor makes an effective front-line detection system. Wireless extends this effectiveness enormously. Here’s why...
Wireless gas sensing lets you...
A wireless gas sensor lets you measure the concentration of a growing variety of gases such as...
Any reactions that were limited by lack of oxygen will, when in an enriched atmosphere of oxygen, speed up – this includes combustion, and the risk of an explosion may increase. Premature oxidation can result.
Carbon Monoxide (CO)
For example, this may come from vehicle emissions in car park buildings.
Carbon Dioxide (CO2)
Carbon Dioxide may be produced by volcanoes. Or encountered in mines where gas sensors are a better alternative to the more traditional canary in a cage.
Carbon Dioxide is used in factories where carbonated drinks are made. It's often used in fire extinguishers and may be used in its solid form, dry ice, for refrigeration.
As its heavier than air, it tends to flow downhill into the lowest places it can get to.
Methane (CH4) and natural gas
This may be encountered in places such as inspection pits and mines, where the risks are explosion, or suffocation due to lack of oxygen.
While methane is found in natural gas, it can also be used to make Acetylene (for welding), Hydrogen and Methanol.
So using a wireless gas sensor system to monitor mines or detect industrial gas leaks is a good way to manage these risks.
Sulphur Dioxide (SO2)
This is the gas that’s notorious for creating the acid rain that dissolves buildings.
It’s mainly produced as an unwanted byproduct of industrial processes such as the manufacture of fumigants, food preservative, bleaching textiles and paper manufacture. The combustion of coal or oil also produces Sulphur Dioxide.
Propane (C3H8) and Butane (C4H10)
For example, these may be used in places such as restaurants and kitchens where they may be used for cooking, or for heating industrial buildings.
Hydrogen Sulphide (H2S)
This gas can build up in buildings that contain livestock.
Sulphur Dioxide may be produced when bacteria break down animal manure. In lower concentrations it can be a general irritant, but in high enough concentrations can be extremely poisonous.
Ammonia is mostly used as a fertilizer but is also used for preserving fruit, killing fungi and for manufacturing some types of plastics and cleaners.
Ozone is just another form of oxygen, but can be very hard on the lungs if you breathe it… it erodes lung tissue if you breathe it in large enough concentrations.
In nature, lightning can create ozone from the oxygen in the air, as can other sparks. Ultraviolet light from the sun, acting on chemicals from car exhausts, can cause ozone levels to build up in an urban environment, during daylight.
Ozone generators are widely used to process wastewater, and where large quantities of ozone are produced, wireless gas sensors may be used for continuous monitoring. In nearly all countries, the maximum safe concentration is 0.05 parts per million.
Volatile Organic Solvents are given off as gases from things such as solvents, used in factories for industrial processes, paint, varnish, lacquer, cleaners, glue and pesticides.
They may also be given off during copying and printing.
General Air Quality
For example, in office buildings or around a city. Air Quality Mapping of cities is starting to gain traction.
Sensing flammable gases
Flammable gases are often used for cooking
or heating, but leaks can be dangerous. A wireless gas sensor can detect these
gases and provide good insurance at a reasonable price and are already
Sensing toxic gases
Carbon monoxide is produced when combustion takes place and there isn’t sufficient oxygen to allow the formation of carbon dioxide.
Sources of carbon monoxide are vehicle exhausts, cigarette smoking and un-vented domestic heating devices such as fires and gas heaters that may also use up the oxygen in a room.
Sensing gases that don’t support life
Carbon Dioxide (CO2) isn’t toxic, but doesn’t support life, unless you happen to be a plant!
As it’s heavier than air, carbon dioxide sinks and accumulates in the lowest places it can get to.
So if you’re a barman, and about to go down into the cellar to see why there’s no carbon dioxide to carbonate the beer at the bar, take care. Carbon Dioxide may be leaking from the cylinder below and you may be about to climb down into an un-breathable atmosphere.
A wireless gas sensor that detects carbon dioxide can be easily installed to protect against this potentially-fatal hazard.
There are a number of things you need to consider before you select a gas sensing system. You'll need to think through all of the steps from what it is you want to measure all the way through to what you want to do with the information.
You need to know about the gas you want to sense and whether there are any potential hazards associated with it, about the environment you want to put the gas sensor into and any health and safety issues with doing it and the suitability of the sensor.
If you want more than just a gas alarm you'll need to think about what to do with the data and how you will maintain your gas sensing system in the years ahead.
Which type of gas do you want to detect?
You’ll need a sensor that’s specifically made to sense this.
What’s the concentration range you want to measure over?
For example, a concentration range of 0 – 200ppm (200 parts of gas per million parts of air) may be appropriate for Carbon Monoxide detection.
Is the target gas flammable?
If so, for safety reasons, it’s essential that the parts of the sensing system that come into contact with any such gas, is rated intrinsically safe. An intrinsically safe device is one where any energy available from the power supply used to power the electronics, or any RF energy from the transmitter, is limited to such a small amount that it couldn’t possibly ignite a flammable gas mixed with air.
In practice, this means there can’t be any chance of a spark or a hotspot developing in the equipment during normal operation or as a result of a malfunction.
Is the gas toxic?
If so, you’ll need to get expert advice on this.
Is the wireless gas sensor waterproof?
If there’s any chance that the sensor will get sprayed with water from time to time it should have a suitable Ingress Protection (IP) rating, or you’ll need to put it into an enclosure to protect it.
The enclosure will need to be vented in some way to allow the gas to flow past the sensor.
Verify the quality of the product.
If your own safety, or the safety of others depends on a gas sensing system it must be reliable. Make sure that it’s well designed and manufactured and be sure to purchase it from a reputable supplier. Check the integrity of the designer/manufacturer. The wireless gas sensor should be designed and manufactured to an international quality standard such as ISO9001.
Is it sensitive enough?
What’s the smallest gas concentration you want to detect? Choose a sensor that’s sensitive enough to detect the smallest gas concentration that you want to measure.
Is it accurate enough?
Check the accuracy in the manufacturer’s specification.
Does it have long-term stability?
Sensor outputs usually drift over time, so be sure to consider the manufacturer’s specification and decide if its stability is good enough for your application.
How often does it need to be calibrated?
No matter how good the stability and accuracy of a gas sensor is, you’ll need to periodically compare the sensor against a traceable reference instrument – one with it’s own current calibration certificate.
In practice, this means using a reference instrument at least five times more accurate than the one you’re checking. The manufacturer should recommend the maximum time between calibration checks.
How much power does it use?
If you have continuous power available, this probably doesn’t matter. However, if the wireless gas sensor will run on batteries, or scavenge energy from the environment, you need to consider the amount of supply current it will use.
You can find this in the manufacturer’s specification. This varies a lot between sensor type and manufacturer, so compare the supply currents of available sensors of the sensor type that suits your needs.
The supply current will usually be specified in milliamps – a milliamp is a thousandth of an Amp and is often abbreviated to mA. The fewer mA, the better. The transmitter shouldn't use much power as it should only transmit briefly and occasionally when it sends the data.
Does the wireless gas sensor respond rapidly enough?
If your gas sensors are part of an early warning system, you want to know when the target gas reaches the alarm threshold, not two minutes after.
Is it robust?
Ensure that it's tough enough to withstand the environment it's to be located in.
Is it resistant to poisoning?
If the surface on which the sensor senses the gas can be easily contaminated, then the sensitivity will reduce and the results will be inconsistent.