How to correctly sample gases using pumped instruments

In many situations, workers must perform pre-entry gas checks, to make sure that a confined space is safe before entering. This is often a requirement arising from risk assessment or to allow the issuing of permits to work, or is simply needed because the area is inherently risky. Whatever the reason, using a pumped device in conjunction with a sampling tube is a great way to perform pre-entry checks to check that a confined space is safe before entry.

However, taking measurements in this way brings its own set of challenges and dangers, and when using Crowcon products in pumped or manual sampling modes, all operators should take care to follow these instructions:

• It is strongly recommended that, before proceeding, a function check is performed using the pump and sample tube with the gas/vapour to be detected.

• To reduce the risk of absorption of the gas/vapour in the sample tube, ensure the temperature of the sampling tube is above the flashpoint temperature of the target vapour.

• Ensure the monitor is correctly calibrated for the target gas/vapour.

• Only use the sample tube supplied by Crowcon. It is strongly recommended that ‘reactive gas tubing’ (part no. AC0301) is used for sampling gases/vapours that are likely to be adsorbed (for example, toluene, chlorine, ammonia, hydrogen sulphide, ozone, hydrogen chloride, NOx, etc).

• Keep the sample tube length as short as possible.

• Please allow sufficient time for the gas/vapour to reach the sensor; allow at least 3 seconds per metre plus the normal T90 response time of the sensor (typically 30–40 seconds).

In addition, please note that some of the gases that can be measured by our gas detection products are classified as ‘reactive’ gases.

A reactive gas will react with, or be absorbed by, the material(s) with which it comes into contact. As a result, the gas concentration reaching the sensor can be reduced, leading to an incorrect reading.

The following list includes some (but not all) reactive gases, which are listed with the appropriate calibration gas. Please contact Crowcon for specific gas concentration information and cross-calibration values).

Target Gas Calibration Gas
Ozone (O3) Ozone (via O3 generator)
Hydrogen Chloride (HCL) Hydrogen Chloride
Hydrogen Fluoride (HF) Hydrogen Chloride or Sulphur Dioxide
Chlorine (Cl2) Chlorine (via Cl2 generator)
Fluorine (F2) Chlorine (via Cl2 generator)
Chlorine Dioxide (ClO2) Chlorine (via Cl2 generator
Phosgene (COCl2) Chlorine (via Cl2 generator)
Sulphur Dioxide (SO2) Sulphur Dioxide
Nitrogen Dioxide (NO2) Nitrogen Dioxide
Nitrogen Monoxide (NO) Nitrogen Monoxide
Ammonia (NH3) Ammonia

• It is very important that the appropriate accessories and precautions are applied when measuring, calibrating or bump testing sensors that are targeting reactive gasses

When taking sample measurements:

• Use Teflon, FEP or PTFE tubing; the tube length must be kept as short as possible (<50 cm). Avoid connectors and unions.
• Allow the sample to flow through the regulator/pipe for at least 3 minutes, for initial absorption to occur, before attempting to get a reading.

When calibrating the above points apply in addition to the following:

• The recommended gas flow-rate is 0.5 litres per minute.
• Gas generators are recommended, instead of gas cylinders, for some very unstable gases, especially where very low ppm concentrations are required.
• Use only stainless steel regulators for cylinder gas.
• Ensure the correct calibration adaptor is used, appropriate to the specific product.

Following the above guidance will allow your pumped devices pre-entry checks to deliver accurate measurements – even with reactive gasses – and will keep staff safe and well.

TWA Resume – how Crowcon’s patented feature keeps workers safe and makes compliance easier

Most people who work with hazardous gases, and particularly anyone with responsibility for regulatory compliance, will be familiar with the various ways of measuring workplace exposures to gas. You may have heard of short- and long-term exposure limits; these are used to quantify the amount of gas a worker can be exposed to without harm, and most gas detectors track them.

But why differentiate between a short-term and long-term exposure? Well, that has mainly to do with the ways in which gases can be harmful. Some gases (hydrogen cyanide, for example) can be almost immediately fatal if inhaled at a given concentration, but some gases remain harmless if present at or below a much lower level for extended periods of time.

If a worker’s long-term exposure is more than the safe level, however, then some gases can be seriously dangerous to health. And the company in charge may become legally liable because it will have failed to comply with gas regulations.

Non-compliance can get very expensive, very quickly. It is costly in both financial and reputational terms.

Figure 1: This image shows how Crowcon’s proprietary TWA Resume feature keeps workers safe and proves a firm’s compliance, by continuing to monitor exposure to harmful gases even after a mid-shift break or other switch-off during the TWA period. Other detectors don’t do this, they assume any switch-off (e.g. for meals or to drive between sites) signals a new period of measurement, which leaves workers vulnerable to over-exposure and harm, and firms open to legal sanctions due to harm and/or non-compliance. In this image, you can see the workplace exposure limit is breached at around 14:00, but only the Crowcon device with TWA Resume alerts the user to this fact and documents it.

Why use TWAs?

Long-term and short-term workplace exposure limits (WELs) for gases are set out by local regulatory bodies. In the UK, the HSE document EH40 applies. Chronic exposure is often measured via a time-weighted average, or TWA. That means the worker’s exposure to a gas is monitored across a given period, usually 8 hours, to make sure the gas(es) remain(s) at or below the WEL throughout that time.

Unfortunately, it is incredibly easy to mess up a TWA measurement and thus fall foul of the regulations. This is because many standard gas detectors erase the TWA timer history when they are switched off, even if the 8-hour/TWA measurement period is ongoing. So, if an operator turns off one of these detectors because they are having lunch or moving between sites, then switches it back on again when they get back to work (bearing in mind this is a continuation of the TWA period they have already begun to track), the detector will assume that they are beginning a new TWA measurement period.

Clearly, this breaches regulations and can be very dangerous – Figure 1, above, shows why. In this example, the worker exceeds the safe limit at around 14:00 but the traditional device does not ‘see’ this or alert them. The Crowcon device with TWA Resume, however, does sound the alert. And that may save both the worker and the company from a great deal of harm.

What is TWA Resume?

The Crowcon T4 and Gas-Pro ranges have Crowon’s proprietary TWA Resume feature. This  innovative and unique functionality makes sure accurate TWAs are recorded for each and every 8-hour/TWA period, keeping employees safe and removing the risk of non-compliance. Furthermore, it makes it easy for a firm to prove their compliance in the face of any legal claim.

TWA Resume is a patented feature only found on Crowcon devices. When turned off during the TWA measurement period, it stores TWA data in its memory. When a worker switches it back on, they can choose to resume measurement from where it left off, or start a new TWA measurement.

T4 and Gas-Pro detectors store this data in their logs, where is available for further analysis and to prove compliance. Even better, TWA alarms and near-miss data can now be easily exported into Crowcon Connect, a cloud-based portal that gives customers total data visibility. This makes it easy for them to prove compliance, and to be sure that their workers are safe.

Because TWA Resume is a patented Crowcon feature, only Crowcon can provide it. If you want to keep your staff safe while making regulatory compliance much easier, please contact us. We’ll be happy to give you more information on our patented TWA resume feature and discuss how it can help you and your business.

Covid-19 is making oxygen management crucial for hospitals

The current Covid-19 pandemic is pushing healthcare to the limit – but oxygen management in hospitals has become a particular challenge for health systems worldwide. Within the healthcare environment, the safety of the healthcare providers and their patients is paramount.

When patients are hospitalised with Covid-19 they often need additional oxygen, and the logistics and sheer volume of this demand is forcing hospitals to take drastic action to manage oxygen use.

A recent BBC documentary, for which a film crew traced the impact of Covid-19 on the Royal Free Hospital in London, clearly shows how the problems of oxygen management are taxing front-line medics and NHS managers, and directly affecting patient care.

At the time of filming, 80% of patients at the Royal Free had Covid-19 and most were on supplementary oxygen at between five and thirty litres per second. As Rui Reis, operations manager for estates at the trust, explains in the film, the hospital used a month’s supply of oxygen in two days and was faced with the prospect of drops in the pressure of patients’ oxygen and in delivery levels – with potentially catastrophic results.

In more normal times, the hospital’s estates management could act to mitigate the problem. But all such actions would require a 4–6-hour shutdown of the oxygen supply.

And in a pandemic, that simply is not an option.

Striking a Balance

The Royal Free had never experienced such oxygen issues before, and soon realised that a balance had to be struck between reducing oxygen use and simultaneously maintaining patient care and the oxygen infrastructure. As a result, they took various measures, for example doctors decided to reduce target blood oxygen levels from 92–94% to 90–94%, while giving clinicians the option to increase oxygen levels in line with patient need. And operations director Rachel Anticoni ensured that every oxygen outlet was closed off where possible to avoid leaks, rather like stopping a dripping tap.

In the film, Rachel Anticoni reports their solutions had reduced oxygen use by around 3,000 litres per minute.

Gas monitoring makes the difference

The Royal Free offers a fine example of how good gas management can improve outcomes and operations. This is something that Crowcon knows about, because we already supply hospitals with our oxygen detectors – these provide early warning of  oxygen-riched environments (which can be an explosion risk) and can also be used to detect the leaks that drain oxygen capacity.

To summarise:

  • The Covid-19 pandemic means that hospitals must now use unprecedented amounts of oxygen.
  • This has caused them to struggle with capacity and mitigate against unnecessary use to ensure supplies are sustainable.
  • Crowcon oxygen detectors can help, by warning hospitals of oxygen leaks and preventing the occurrence of oxygen-rich environments.
  • In this way, gas monitoring protects health system resources and patients alike.

Find out more about Oxygen risks in healthcare environments in our infographic here.

If you want to know how we can help with monitoring oxygen use to ensure supply or prevent oxygen rich environments pose an explosion risk, our experts can help, please get in touch.

Are you safe to re-start operations?




-Car plants

-Manufacturing facilities of all types

-Bars, restaurants and hospitality venues

-Leisure centres and swimming pools



-Schools and colleges


What are the dangers?





What should I do before re-starting operations?




What’s the difference between a pellistor and an IR sensor?

Sensors play a key role when it comes to monitoring flammable gases and vapours. Environment, response time and temperature range are just some of the things to consider when deciding which technology is best.

In this blog, we’re highlighting the differences between pellistor (catalytic) sensors and infrared (IR) sensors, why there are pros and cons to both technologies, and how to know which is best to suit different environments.

Pellistor sensor

A pellistor gas sensor is a device used to detect combustible gases or vapours that fall within the explosive range to warn of rising gas levels. The sensor is a coil of platinum wire with a catalyst inserted inside to form a small active bead which lowers the temperature at which gas ignites around it. When a combustible gas is present the temperature and resistance of the bead increases in relation to the resistance of the inert reference bead. The difference in resistance can be measured, allowing measurement of gas present. Because of the catalysts and beads, a pellistor sensor is also known as a catalytic or catalytic bead sensor.

Originally created in the 1960’s by British scientist and inventor, Alan Baker, pellistor sensors were initially designed as a solution to the long-running flame safety lamp and canary techniques. More recently, the devices are used in industrial and underground applications such as mines or tunnelling, oil refineries and oil rigs.

Pellistor sensors are relatively lower in cost due to differences in the level of technology in comparison to IR sensors, however they may be required to be replaced more frequently.

With a linear output corresponding to the gas concentration, correction factors can be used to calculate the approximate response of pellistors to other flammable gases, which can make pellistors a good choice when there are multiple flammable vapours present.

Not only this but pellistors within fixed detectors with mV bridge outputs such as the Xgard type 3 are highly suited to areas that are hard to reach as calibration adjustments can take place at the local control panel.

On the other hand, pellistors struggle in environments where there is low or little oxygen, as the combustion process by which they work, requires oxygen. For this reason, confined space instruments which contain catalytic pellistor type LEL sensors often include a sensor for measuring oxygen.

In environments where compounds contain silicon, lead, sulphur and phosphates the sensor is susceptible to poisoning (irreversible loss of sensitivity) or inhibition (reversible loss of sensitivity), which can be a hazard to people in the workplace.

If exposed to high gas concentrations, pellistor sensors can be damaged. In such situations, pellistors do not ‘fail safe’, meaning no notification is given when an instrument fault is detected. Any fault can only be identified through bump testing prior to each use to ensure that performance is not being degraded.


IR sensor

Infrared sensor technology is based on the principle that Infrared (IR) light of a particular wavelength will be absorbed by the target gas. Typically there are two emitters within a sensor generating beams of IR light: a measurement beam with a wavelength that will be absorbed by the target gas, and a reference beam which will not be absorbed. Each beam is of equal intensity and is deflected by a mirror inside the sensor onto a photo-receiver. The resulting difference in intensity, between the reference and measurement beam, in the presence of the target gas is used to measure the concentration of gas present.

In many cases, infrared (IR) sensor technology can have a number of advantages over pellistors or be more reliable in areas where pellistor-based sensor performance can be impaired- including low oxygen and inert environments. Just the beam of infrared interacts with the surrounding gas molecules, giving the sensor the advantage of not facing the threat of poisoning or inhibition.

IR technology provides fail-safe testing. This means that if the infrared beam was to fail, the user would be notified of this fault.

Gas-Pro TK uses a dual IR sensor – the best technology for the specialist environments where standard gas detectors just won’t work, whether tank purging or gas freeing.

An example of one of our IR based detectors is the Crowcon Gas-Pro IR, ideal for the oil and gas industry, with the availability to detect methane, pentane or propane in potentially explosive, low oxygen environments where pellistor sensors may struggle. We also use a dual range %LEL and %Volume sensor in our Gas-Pro TK, which is suitable for measuring and switching between both measurements so it’s always safely operating to the correct parameter.

However, IR sensors aren’t all perfect as they only have a linear output to target gas; the response of an IR sensor to other flammable vapours then the target gas will be non-linear.

Like pellistors are susceptible to poisoning, IR sensors are susceptible to severe mechanical and thermal shock and also strongly affected by gross pressure changes. Additionally, infrared sensors cannot be used to detect Hydrogen gas, therefore we suggest using pellistors or electromechanical sensors in this circumstance.

The prime objective for safety is to select the best detection technology to minimise hazards in the workplace. We hope that by clearly identifying the differences between these two sensors we can raise awareness on how various industrial and hazardous environments can remain safe.

For further guidance on pellistor and IR sensors, you can download our whitepaper which includes illustrations and diagrams to help determine the best technology for your application.

You won’t find Crowcon sensors sleeping on the job

MOS (metal oxide semiconductor) sensors have been seen as one of the most recent solutions for tackling detection of hydrogen sulphide (H2S) in fluctuating temperatures from up to 50°C down to the mid-twenties, as well as humid climates such as the Middle East.

However, users and gas detection professionals have realised MOS sensors are not the most reliable detection technology. This blog covers why this technology can prove difficult to maintain and what issues users can face.

One of the major drawbacks of the technology is the liability of the sensor “going to sleep” when it doesn’t encounter gas for a period of time. Of course, this is a huge safety risk for workers in the area… no-one wants to face a gas detector that ultimately doesn’t detect gas.

MOS sensors require a heater to equalise, enabling them to produce a consistent reading. However, when initially switched on, the heater takes time to warm up, causing a significant delay between turning on the sensors and it responding to hazardous gas. MOS manufacturers therefore recommend users to allow the sensor to equilibrate for 24-48 hours before calibration. Some users may find this a hinderance for production, as well as extended time for servicing and maintenance.

The heater delay isn’t the only problem. It uses a lot of power which poses an additional issue of dramatic changes of temperature in the DC power cable, causing changes in voltage as the detector head and inaccuracies in gas level reading. 

As its metal oxide semiconductor name suggests, the sensors are based around semiconductors which are recognised to drift with changes in humidity- something that is not ideal for the humid Middle Eastern climate. In other industries, semiconductors are often encased in epoxy resin to avoid this, however in a gas sensor this coating would the gas detection mechanism as the gas couldn’t reach the semiconductor. The device is also open to the acidic environment created by the local sand in the Middle East, effecting conductivity and accuracy of gas read-out.

Another significant safety implication of a MOS sensor is that with output at near-zero levels of H2S can be false alarms. Often the sensor is used with a level of “zero suppression” at the control panel. This means that the control panel may show a zero read-out for some time after levels of H2S have begun to rise. This late registering of low-level gas presence can then delay the warning of a serious gas leak, opportunity for evacuation and the extreme risk of lives.

MOS sensors excel in reacting quickly to H2S, therefore the need for a sinter counteracts this benefit. Due to H2S being a “sticky” gas, it is able to be adsorbed onto surfaces including those of sinters, in result slowing down the rate at which gas reaches the detection surface.

To tackle the drawbacks of MOS sensors, we’ve revisited and improved on the electrochemical technology with our new High Temperature (HT) H2S sensor for XgardIQ. The new developments of our sensor allow operation of up to 70°C at 0-95%rh- a significant difference against other manufacturers claiming detection of up to 60°C, especially under the harsh Middle Eastern environments.

Our new HT H2S sensor has been proven to be a reliable and resilient solution for the detection of H2S at high temperatures- a solution that doesn’t fall asleep on the job!

Click here for more information on our new High Temperature (HT) H2S sensor for XgardIQ.

An ingenious solution to the problem of high temperature H2S

Due to extreme heat in the Middle East climbing up to 50°C in the height of summer, the necessity for reliable gas detection is critical. In this blog, we’re focusing on the requirement for detection of hydrogen sulphide (H2S)- a long running challenge for the Middle East’s gas detection industry.

By combining a new trick with old technology, we’ve got the answer to reliable gas detection for environments in the harsh Middle Eastern climate. Our new High Temperature (HT) H2S sensor for XgardIQ has been revisited and improved by our team of Crowcon experts by using a combination of two ingenious adaptations to its original design.

In traditional H2S sensors, detection is based on electrochemical technology, where electrodes are used to detect changes induced in an electrolyte by the presence of the target gas. However, high temperatures combined with low humidity causes the electrolyte to dry out, impairing sensor performance so that the sensor has to be replaced regularly; meaning high replacement costs, time and efforts.

Making the new sensor so advanced from its predecessor is its ability to retain the moisture levels within the sensor, preventing evaporation even in high temperature climates. The updated sensor is based on electrolytic gel, adapted to make it more hygroscopic and avoiding dehydration for longer.

As well as this, the pore in the sensor housing has been reduced, limiting the moisture from escaping. This chart indicated weight loss which is indicative of moisture loss. When stored at 55°C or 65°C for a year just 3% of weight is lost. Another typical sensor would lose 50% of its weight in 100 days in the same conditions.

For optimal leak detection, our remarkable new sensor also features an optional remote sensor housing, while the transmitter’s displays screen and push-button controls are positioned for safe and easy access for operators up to 15metres away.


The results of our new HT H2S sensor for XgardIQ speak for themselves, with an operating environment of up to 70°C at 0-95%rh, as well featuring a 0-200ppm and T90 response time of less than 30 seconds. Unlike other sensors for detecting H2S, it offers a life expectancy of over 24 months, even in tough climates like the Middle East.

The answer to the Middle East’s gas detection challenges fall in the hands of our new sensor, providing its users with cost-effective and reliable performance.

Click here for more information about the Crowcon HT H2S sensor.

Once again, Gas-Pro is ‘detector of choice’ for volcano environmental expedition

We are all familiar with the term global warming and often see statistics about the potential effects this could have on our planet.  One such prediction is by the end of this century the globe will increase in temperature by between 0.8 and 4 degrees.

What many of us may not know is that volcanoes, which are a completely natural phenomenon, contribute a significant amount of gases into our atmosphere. And these gases are currently not considered in the world’s climate models, which means there is potentially a large margin of error.

However, this could be about to change as Yves Moussallam, an inspiring French Volcanologist, who with the support of Rolex and the 2019 Rolex Awards for Enterprise, has made it his mission to understand volcanos and how they impact on our planet.  He ventures into these dramatic and dangerous environments to take measurements which are used by scientists and climatologists to improve their prediction models.

By observing volcanos, and gathering this vitally important data, he is helping the world understand the impact volcanos are having on climate change.

Yves is no stranger to volcanic expeditions. In 2015, he led a small team to the Nazca subduction zone in South America. Their mission was to provide the first accurate and large-scale estimate of the flux of several volatile gas species.

To keep the team safe, Yves selected Crowcon detection equipment and was delighted with Gas man and Gas-Pro’s lightweight, clean and safe functionality.

Now Yves is back with a new expedition and has turned to Crowcon once again. This time, Yves is heading to the region of Melanesia in Italy.  Satellites, which are used to track volcanic behaviour, have shown that this region is responsible for approximately a third of global volcanic gas emissions.

His expedition will climb these volcanoes and take measurements directly in the volcanic plume.

There are two main methods to measure gases in volcanoes.  The first is via satellite which takes images from space.  The second is to go directly into the field and measure gas released at its source.

Experts believe the method of working directly in the field is the most accurate as it is positioned far closer to the source so there is a reduced risk of error.

To conduct these measurements requires tried, tested and trusted equipment and with Crowcon’s proven track record, Yves turned again to Gas-Pro.

Crowcon’s Gas-Pro includes an onboard datalogging feature which will provide an extra line of data and an idea of average exposure, which is important for expeditions that span longer periods.  It is also lightweight which is hugely beneficial when carrying bulky equipment.

Everyone at Crowcon wishes Yves a safe and successful expedition and we hope the data he gathers will help us understand the impact volcanos have on our world.

#Rolex #RolexAwards #PerpetualPlanet #Perpetual

Helping you stay safe during the BBQ season








Quick facts and tips about BBQ charcoals:



Quick facts and tips about gas cannisters:

  • Always keep the cannister away from ignition sources when changing cannisters


Chernobyl – a powerful safety message to the world

The recent Sky Atlantic TV series Chernobyl sent out a powerful message about the catastrophic and far reaching consequences of radiation gases, both to people and the environment.

The series is based on true events from the 1986 nuclear disaster in the then USSR; the largest uncontrolled radioactive release into the environment ever recorded. The accident resulted in an untold number of fatalities, as well as serious social and economic disruption for large populations within the USSR and beyond.

The Chernobyl explosion resulted in a radioactive gas cloud which travelled across Europe, including the UK; falling to the ground in the form of ‘nuclear rain’.

There are many disturbing facts we read about. Not least that according to the British Ministry of Health, 369 farms and 190,000 sheep in Britain still contain traces of radioactive fallout from the Chernobyl disaster.

Both human and mechanical error contributed to the disaster and thankfully safety standards, regulations, awareness and new technologies have significantly improved since the disaster.

The principal of safety, whether a huge nuclear facility or small manufacturing plant, must remain the same. Here at Crowcon we are dedicated to keeping people and the environment protected. Our technologies support organisations across multiple industries, including nuclear plants, improving plant and personal safety. Our technologies help our customers be protected from the dangers of gases.

At Crowcon, we welcome shows such as Chernobyl which document historical disasters such as this and highlight in a dramatic but real way, the importance of ensuring companies understand the need for safety measures, however big or small, are in place.  Protecting their people, the environment and the world.