How VOCs affect air quality, health and the environment – Part 1

The term VOC (Volatile Organic Compound) refers to a wide range of carbon-containing chemical compounds. At room temperature, VOCs tend to be liquid or solid, with a high vapour pressure that means they readily vaporise into gaseous states. In recent years, increasing attention has been paid to VOCs as pollutants and health hazards. This blog will provide an introduction to VOCs and their effects on human health and the environment, and give an overview of regulations on VOC emission.

Sources of VOC in air

VOC exist naturally in the atmosphere through processes including vegetation growth and soil activity, as well as in biomass burning. However, a significant portion of VOC build-up in the atmosphere come from man-made sources; these include emissions from road traffic and from chemical processes such as crude oil cracking; and products that emit high concentrations of VOCs (for example, paint, solvents and varnishes).

Effects of VOCs on human health

The effects of VOC emissions on human health varies widely according to context. Some VOCs are harmless, but many are toxic at low levels, while others are flammable at higher concentrations. Repeated and long-term, low-level exposure to harmful VOCs can cause serious health issues. For example, formaldehyde, styrene, benzene and other aromatics are known carcinogens – thus, exposure to traffic exhaust fumes, smoking and strong solvents can present serious health risks. Growing awareness of the chronic toxicity of VOCs has led to reduced occupational exposure limits (OEL) and increased requirements for direct measurement.

You can read more about the dangers of VOCs in our white paper.

Environmental issues caused by VOCs

Aside from adverse health implications, the emission of VOCs into the atmosphere causes serious environmental issues. One of these is the formation of ground-level ozone, which leads to smog.

Normally, ozone (or O3) is naturally formed at high altitude in the atmosphere (stratosphere) when O2 molecules are separated into individual oxygen particles by UV radiation. These free oxygen particles then collide with other O2 molecules to become ozone. While we know that ozone helps to protect our planet from the sun’s harmful UV rays, tropospheric, or ground-level, ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs).

Here is an example of how nitrogen dioxide can lead to the creation of ozone:

NO2 + Sunlight (UV rays) = NO + O

The free oxygen particle then attaches itself to an O2 molecule and becomes ozone. This happens when pollutants emitted by vehicles, power plants, chemical plants and other sources chemically react in the presence of sunlight. Breathing ozone can cause respiratory irritation and may exacerbate respiratory diseases such as bronchitis and asthma. Ozone at ground-level is hazardous to plants and negatively affects crops.

In addition to ground-level ozone formation, some VOCs may cause odour problems, due to their high odour intensity. Processes like waste incineration, food processing and wastewater treatment emit lots of malodorous gases and are often subject to odour nuisance complaints from nearby residents. Foul smelling gases including H2S, NH3 and VOCs are a significant problem for many industries, including the pharmaceutical, food and beverage, textile and tannery sectors.

At high concentrations, foul-smelling VOCs can cause dizziness and respiratory issues. For this reason, regulations are in place to reduce VOCs in ambient air.

Directives and regulations on VOC emission

Most countries have directives and regulations on VOC emission. In Europe, the relevant directives on atmospheric pollutants, including VOC emissions, are 2001/81/EC and 2016/2284. The first directive sets national emissions ceilings for the VOC emission from all sources, which were to be reached by the year 2010. The second directive specifies the percentage reduction in VOC emissions, both for the individual country and the EU as an entire area.

In addition to outdoor VOC emissions, many countries have implemented regulations to limit the use of VOCs in consumer products. In the EU, Directive 2004/42/EC specifies emission limits for VOCs, prompted by the use of organic solvents in decorative paints and varnishes and in vehicle refinishing products. The directive sets the maximum permissible contents of VOCs in g/L. The directive also requires that suppliers label the subcategory of the product, defines the legal limit value for VOC contents and gives the maximum content of VOC permissible for the product in its ready-to-use condition.
In our next blog we will discuss Crowcon’s unique solution for VOC detection in ambient air.
References
1. Odor-causing volatile organic compounds in wastewater treatment plant units and sludge management areas (J Environ Sci Health A Tox Hazard Subst Environ Eng. 2008 Nov)
2. Ground-level ozone basics (US Environmental Protection Agency guide)
3. Do volatile organic compounds smell? (Foobot website)
4. Volatile organic compounds (VOC) and consumer products regulations (Chem Safety Pro website)
5. Effective and sustainable VOC removal with ozone and AOP (Ozonetech website)

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Improving Hydrogen Leak Detection to Increase PEM Fuel Cell & Electrolysis Efficiency

Co-edited by Alicat & Crowcon

Amidst the global push for sustainable, carbon neutral energy sources, many corporations and countries are increasingly interested in alternative fuels. One such fuel is hydrogen, playing a vital role in the clean energy landscape as a green alternative to natural gas. This has resulted in a sudden increased interest in fuel cell and electrolysis technology.

One of the primary challenges facing both of these processes is hydrogen leakage. Hydrogen gas requires careful control on the input side of PEM fuel cell stacks and on the output side of electrolysis. Any leakage that occurs not only diminishes efficiency, but also raises costs and introduces potential hazards such as flammability and asphyxiation.

Here we discuss hydrogen leak detection in more detail and provide several solutions to help improve the safety and efficiency of fuel cell processes.

Why hydrogen leaks in fuel cells

H₂ gas has a high propensity to leak due to its very small size and its low density (0.09 g/L at NTP of 0°C / 1 atm) which corresponds to a high buoyancy.

In fuel cell stacks, hydrogen is prone to leak from seals present at process connections near the H₂ storage cylinders and associated flow paths. While it is nearly impossible to reach 100% gas containment in a fuel cell stack, reliable leak detection is essential for minimizing loss.

Detecting hydrogen leaks is critical to maintaining process & personnel safety

Not only does leakage decrease process efficiency, but it becomes a serious safety concern. Hydrogen has a Lower Explosive Limit (LEL) of just 4% volume, meaning even tiny quantities of H₂ can cause explosions when mixed with atmospheric air. Even a spark of static electricity from a person’s finger is enough to trigger an explosion when hydrogen is present.

Since hydrogen is odorless, colorless, and tasteless, hydrogen leak detection is extremely difficult without the help of mechanical sensors. Monitoring H₂ therefore demands specialized equipment to alert personnel of danger and prompt emergency response procedures.

Detecting hydrogen with traditional sensor technology

Traditional sensor technologies for flammable gas detection are pellistors. Their key disadvantage is that they require oxygen, making them unsuitable in some installations. Another challenge is that some applications put pellistors at risk of being poisoned or inhibited, leaving workers unprotected. These sensors are not fail-safe, and a failure will not be detected unless test gas is applied, commonly known as a bump test.

Detection with mass flow instruments

Hydrogen leak detection relies on in-line process instruments and careful monitoring of system inputs and outputs. For PEM electrolysis, one method involves comparing the mass flow rates of H₂O input and hydrogen output to calculate the amount of leakage occurring during the process. Coriolis instruments are ideal for measuring and controlling the input H₂O for such electrolysis systems.

Fuel cell stack leak check test bench

Figure 1. Fuel cell stack leak check test bench

For PEM fuel cell stack systems, one common hydrogen leak detection method involves employing a combination of hydrogen sensors alongside flow meters. A flow meter situated downstream of the H₂ supply and measurements can be used in conjunction with hydrogen sensors to detect any leaks on the anode side of a PEM fuel cell stack.

Differential pressure based mass flow instruments enable rapid response times, allowing real time leak detection. Given their sensitivity, they are also able to measure very small leaks with high precision and accuracy. This can help identify points of leakage to improve overall process efficiency, decrease cost, and reduce risks of danger to operators.

Detection with MPS™ technology

Crowcon's Xgard Bright

Figure 2. Crowcon’s Xgard Bright

Crowcon, another Halma company, also has a wide range of products for the detection of hydrogen. The Xgard Bright utilizes their latest technology, the Molecular Property Spectrometer (MPS™), to detect and measure ambient levels of hydrogen and other flammable gases with high-accuracy and precision in real time. Furthermore, the sensors do not require recalibration, significantly reducing total cost of ownership and limiting interaction with the units. The Xgard Bight ensures process operators are at no risk of being poisoned while also guaranteeing no false alarms.

Alicat, Crowcon, and the Halma family of brands are here to provide solutions to help create a safer, cleaner, healthier world.

As always, contact our team at any time to help find the right solution for you.

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How Hydrogen is Helping the Gas and Steel Industries to Go Green

Green hydrogen, taken from both low carbon and renewable energy sources, can play a crucial role in taking a company – or a country – closer to carbon neutrality. Common applications in which green hydrogen can be used include:

Fuel cells for electric vehicles
As the hydrogen in pipeline gas blending
In ‘green steel’ refineries that burn hydrogen as a heat source rather than coal
In container ships powered by liquid ammonia that is made from hydrogen
In hydrogen-powered electricity turbines that can generate electricity at times of peak demand

This post will explore the use of hydrogen in pipeline gas blending and green steel refineries.

Injecting hydrogen into pipelines

Governments and utilities companies worldwide are exploring the possibilities of injecting hydrogen into their natural gas grids, to reduce fossil fuel consumption and limit emissions. Indeed, hydrogen injection into pipelines now features in the national hydrogen strategies of the EU, Australia and the UK, with the EU’s hydrogen strategy specifying the introduction of hydrogen into national gas grids by 2050.

From an environmental point of view, adding hydrogen to natural gas has the potential to significantly reduce greenhouse gas emissions, but to achieve that, the hydrogen must be produced from low-carbon energy sources and renewables. For example, hydrogen generated from electrolysis, bio-waste or fossil fuel sources that use carbon capture and storage (CCS).

In a similar way, countries aspiring to develop a green hydrogen economy can turn to grid injection to stimulate investment and develop new markets. In an effort to kick start its renewable hydrogen plan, Western Australia is planning to introduce at least 10% renewable hydrogen into its gas pipelines and networks, and to bring forward the state’s targets under its renewable hydrogen strategy from 2040 to 2030.

On a volumetric basis, hydrogen has a much lower energy density than natural gas, so end-users of a blended gas would require a higher volume of gas to achieve the same heating value as those using pure natural gas. Simply put, a 5% blending of hydrogen by volume does not directly translate into a 5% reduction in fossil fuel consumption.

Is there any safety risk in hydrogen blending in our gas supply? Let’s examine the risk:

Hydrogen has lower LEL than natural gas, so there is a higher risk of generating a flammable atmosphere with blended gas mixtures.
Hydrogen has lower ignition energy than natural gas and a broad flammable range (4% to 74% in air), so there is higher risk of explosion
Hydrogen molecules are small and move quickly, so any blended gas leak will spread faster and wider than would be the case with natural gas.

In the UK, domestic and industrial heating accounts for half of the UK’s energy consumption and one third of its carbon emissions. Since 2019, the UK’s first project to inject hydrogen into the gas grid has been underway, with trials taking place at Keele University. The HyDeploy project aims to inject up to 20% hydrogen and blend it with the existing gas supply to heat residential blocks and campuses without changing the gas-fired appliances or piping. In this project, Crowcon gas detectors and flue gas analyser are being used to identify the impact of hydrogen blending in terms of gas leak detection. Crowcon’s Sprint Pro flue gas analyser is being used to assess for boiler efficiency.

Crowcon’s Sprint Pro is a professional grade flue gas analyser, with features tailored to meet the needs of the HVAC professional, a robust design, full selection of accessories and 5-year warranty. Read more about the Sprint Pro here.

Hydrogen in the steel industry

Traditional iron and steel production is considered one of the largest emitters of environmental pollutants, including greenhouse gases and fine dust. Steel making processes rely heavily on fossil fuels, with coal products accounting for 78% of these. It is thus not surprising that the steel industry emits around 10% of all global process- and energy-related CO2 emissions.

Hydrogen may be an alternative for steel companies seeking to drastically reduce their carbon emissions. Several steel makers in Germany and Korea are already cutting emissions through a hydrogen reduction steelmaking method that uses hydrogen, not coal, to make steel. Traditionally, a significant amount of hydrogen gas is produced in steel making as a by-product called coke gas. By passing that coke gas through a process called carbon capture and storage (CCS), steel plants can produce significant amount of blue hydrogen, which can then be used to control temperatures and prevent oxidation during steel production.

In addition, steel makers are producing steel products specifically for hydrogen. As part of its new vision of becoming a green hydrogen enterprise, Korean steelmaker POSCO has invested heavily to develop steel products for use in the production, transport, storage and utilisation of hydrogen.

With many flammable and toxic gas hazards being present in steel plants, it is important to understand the cross sensitivity of gases, because a false gas reading could prove fatal. For example, a blast furnace produces a great deal of hot, dusty, toxic and flammable gas consisting of carbon monoxide (CO) with some hydrogen. Gas detection manufacturers that have experience in these environments are well acquainted with the issue of hydrogen affecting electrochemical CO sensors, and thus provide hydrogen-filtered sensors as standard to steel facilities.

To learn more about cross sensitivity, please see our blog. Crowcon gas detectors are used in many steel facilities across the world, and you can find out more about Crowcon solutions in the steel industry here.

References:

Injecting hydrogen in natural gas grids could provide steady demand the sector needs to develop (S&P Global Platts, 19 May 2020)
Western Australia pumps $22m into hydrogen action plan (Power Engineering, 14 Sep 2020)
Green Hydrogen in Natural Gas Pipelines: Decarbonization Solution or Pipe Dream? (Green Tech Media, 20 Nov 2020)
Could hydrogen piggyback on natural gas infrastructure? (Network Online, 17 Mar 2016)
Steel, Hydrogen and Renewables: Strange Bedfellows? Maybe Not… (Forbes.com, 15 May 2020)
POSCO to Expand Hydrogen Production to 5 Mil. Tons by 2050 (Business Korea, 14 Dec 202 0)http://https://www.crowcon.com/wp-content/uploads/2020/07/shutterstock_607164341-scaled.jpg

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The Many Colours of Hydrogen

Hydrogen, alongside other renewables and natural gas has an increasingly vital role to play in the clean energy landscape. Corporations and countries are increasingly interested in alternative fuels amid the global push for carbon neutrality. This year the EU pledged to become climate neutral (that is, to become an economy with net-zero greenhouse gas emissions) by 2050, Australia launched its National Hydrogen Strategy to accelerate development of clean hydrogen and export it to neighbouring countries and Shell and BP pledged to achieve carbon neutrality by 2050.

For many oil and gas companies aiming to decarbonise, hydrogen is a fuel of choice to comply with climate targets. The growth of hydrogen is expected to take off in the next 10–20 years, with costs driven down as hydrogen becomes more widely produced. With new applications, the low-carbon hydrogen market size could reach US$ 25 billion by 2030 and grow even further long-term.

Hydrogen burns clean when mixed with oxygen, and is seen as green fuel alternative in transport, shipping and heating (both domestic and industrial). Interestingly, the use of hydrogen as fuel is not new. Hydrogen is already a component of rocket fuel and is used in gas turbines to produce electricity, or burned to run combustion engines for power generation. Hydrogen is also used as feedstock to produce ammonia, methanol and other petrochemicals.

In general, we know that hydrogen is a good choice of fuel for industries looking to decarbonise, but not all hydrogen is created equal. Although the gas only emits water when burned, its contribution to carbon neutrality depends on how it is produced.

Brown hydrogen is made from the gasification of coal, which emits CO₂ into the air as it combusts. Grey hydrogen is hydrogen produced using fossil fuels, such as natural gas, and is the most commonly-produced form of hydrogen in the world today. Blue hydrogen is made in the same way as grey, but carbon capture and storage (CCS) technologies prevent the release of CO₂, enabling the captured carbon to be safely stored deep underground or used in industrial processes. Turquoise (or low carbon) H₂ is hydrogen produced from natural gas using molten metal pyrolysis technology.

As its name suggests, green or renewable hydrogen is the cleanest variety, producing zero carbon emissions. It is produced using electrolysis powered by renewable energy, like wind or solar power, to produce a clean and sustainable fuel.

Electrolysis splits water (H₂O) into hydrogen and oxygen, so there is no waste and all parts are used with zero environmental impact. If the energy used for electrolysis is taken from renewable sources this can be counted as ‘green fuel’ because there are no negative impacts on the environment.

In our next blog we will discuss the potential hazards of hydrogen that may occur during production, storage and transport, and the gas detection solutions that Crowcon offers.

To learn more download our Hydrogen fact sheet here.

References:

Committing to climate-neutrality by 2050: Commission proposes European Climate Law and consults on the European Climate Pact (Apr 2020)

Shell unveils plans to become net-zero carbon company by 2050 (The Guardian, 16 Apr 2020)

BP sets ambition for net zero by 2050, fundamentally changing organisation to deliver (BP.com, 12 Feb 2020)

Shaping tomorrow’s global hydrogen market (Baker Mackenzie, Jan 2020)

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The Dangers of Hydrogen

As a fuel, hydrogen is highly flammable and so hydrogen leaks generate a serious risk of fire. However, hydrogen fires are markedly different to fires involving other fuels. When heavier fuels and hydrocarbons, like petrol or diesel, leak they pool close to the ground. In contrast, hydrogen is one of the lightest elements on earth, so when a leak occurs hydrogen rapidly disperses upwards. This makes ignition less likely, but a further difference is that hydrogen ignites and burns more easily than petrol or diesel. In fact, even a spark of static electricity from a person’s finger is enough to set off an explosion when hydrogen is available. Hydrogen flame is also invisible, so it is hard to pin-point where is the actual ‘fire’ is, but it generates a low radiant heat due to the absence of carbon and tends to burn out quickly.

Hydrogen is odourless, colourless and tasteless, so leaks are hard to detect using human senses alone. Hydrogen is non-toxic, but in indoor environments like battery storage rooms, hydrogen may build up and cause asphyxiation by displacing oxygen. This danger can be offset to some extent by adding odorants to hydrogen fuel, giving it an artificial smell and alerting users in case of a leak. But as hydrogen disperses quickly, the odorant is unlikely to travel with it. Hydrogen leaking indoors quickly collects, initially at ceiling level and eventually fills up the room. Therefore, the placement of gas detectors is key in early detection of a hydrogen leak.

Hydrogen is usually stored and transported in liquified hydrogen tanks. The last concern is that because it is compressed, liquid hydrogen is extremely cold. If hydrogen should escape from its tank and come in contact with skin it can cause severe frostbite, or even the loss of extremities.

Which sensor technology is best for detecting hydrogen?

Crowcon has a wide range of products for the detection of hydrogen. The traditional sensor technologies for flammable gas detection are pellistors and infrared (IR). Pellistor gas sensors (also called catalytic bead gas sensors) have been the primary technology for detecting flammable gases since the 1960s and you can read our blog to find out on how pellistor sensors work. However, their key disadvantage is that in low oxygen environments, pellistor sensors will not function properly and may even fail. In some installations, pellistors are at risk of being poisoned or inhibited, which leaves workers unprotected. Also, pellistor sensors are not fail-safe, and a sensor failure will not be detected unless test gas is applied.

Infrared-type sensors are a reliable way to detect flammable hydrocarbons in low oxygen environments. They are not susceptible to being poisoned, so IR can significantly enhance safety in these conditions. Read more about IR sensors in our blog, and the differences between pellistors and IR sensors in the following blog.

Just as pellistors are susceptible to poisoning, IR sensors are susceptible to severe mechanical and thermal shock and are also strongly affected by gross pressure changes. Additionally, IR sensors cannot be used to detect hydrogen. So the best option for hydrogen flammable gas detection is molecular property spectrometer (MPS™) sensor technology. This does not require calibration throughout the life cycle of the sensor, and since MPS detects flammable gases without the risk of poisoning or false alarms, it can significantly save on total cost of ownership and reduce interaction with units, resulting in peace of mind and less risk for operators. Molecular property spectrometer gas detection was developed at the University of Nevada and is currently the only gas detection technology able to detect multiple flammable gases, including hydrogen, simultaneously, very accurately and with a single sensor.

Read our white paper to find out more.

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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.

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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.

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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.

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Are you safe to re-start operations?

As governments around the world ease lockdown measures that were introduced to combat Covid-19, many of us are starting to plan how to return to business. But re-starting operations after a break can present specific gas-related problems and dangers that must be dealt with before operations begin.

A terrible example of what can happen otherwise has recently occurred in India. There, a persistent styrene leak, from a factory that had been closed due to the Covid-19 outbreak, killed at least 11 people, and harmed many more within a radius of several kilometres.

The need to check gas safety after a break in operations applies across many sectors. These include:

-Car plants

-Manufacturing facilities of all types

-Bars, restaurants and hospitality venues

-Leisure centres and swimming pools

-Refineries and chemical processing plants, where operations have been scaled back or stopped due to reduced demand

-Laboratories

-Schools and colleges

-General industrial sites that ceased operations due to Covid-19.

What are the dangers?

While the challenges arising will vary by sector, the most common include:

Re-pressurisation of systems. Many industries – from schools and colleges to bars and oil refineries – use pressurised systems or equipment such as boilers, steam heating systems, autoclaves, pipework, heat exchangers and refrigeration plant. If these are not correctly pressurised, they may explode, leak or cause contact injuries Any break in operations may have caused or coincided with a change (usually a drop) in pressure.

Some systems contain gases that are inherently toxic/flammable, some gases may be safe in normal process conditions but are now less safe due to changes in pressure or other conditions created by a recent shut-down. In any case, there is a legal duty to maintain pressurised systems (you can find out more from the HSE’s pages here) so it makes sense to check the system before re-starting operations, and to re-pressurise the system if required.

Areas used to store toxic and/or flammable gases that have not been entered for some time. This is likely to be a widespread danger because such areas are not always industrial. Swimming pool operators store chlorine; cafes, schools and colleges store gases for educational and catering purposes; food-makers, pubs and bars use gases in the manufacture and dispensing of beverages. If gas has leaked during a Covid-19 shut-down, it may endanger property and staff when operations begin again. Alternatively, the break could mean that gases are no longer stored at their optimum pressure or temperature.
It should also be noted that some stored goods may emit toxic or flammable gases if they have been left for a long period. For example, methane and hydrogen sulphide may be generated by organic matter that has begun to degrade or ferment.
Re-starting production or operations where materials/chemicals have been left unattended for some time can also be hazardous. For example, anything stored at a specific pressure may have experienced a change in that pressure, and materials stored in sub-optimal conditions (e.g. in terms of ambient temperature, pressure, exposure to light or operation) may now be unfit for purpose or even dangerous.

What should I do before re-starting operations?

Gas hazards should form part of your re-starting operations risk assessment.

When it comes to gas, Crowcon has a wealth of knowledge gathered over many years and from many installations. If you need reliable information about the gas-related dangers that may arise on your own return to operations, check out our ‘Talking Gas’ information hub, which is full of free resources to download, and our ‘Insights’ knowledge base. And if you have any other questions relating to the post-Covid return, please get in touch.

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How aware of cross-sensitivities when using gas detectors are you?

In a perfect world, gas detector sensors would identify, isolate and measure specific gases and give precise readings for each gas in any context. Unfortunately, technology allows us to come close to that but not to achieve it completely. That is why, when dealing with electrochemical toxic sensors, we have the challenge of cross-sensitivities, sometimes known as ‘interfering gasses’.

Gas detectors generally detect a specified gas and give an alarm and/or reading in proportion to the level present. Cross-sensitivity occurs when a gas other than the gas being monitored/detected can affect the reading given by an electrochemical sensor. This causes the electrode within the sensor to react even if the target gas is not actually present, or it causes an otherwise inaccurate reading and/or alarm for that gas. Obviously, this puts the person using the sensor at risk.

Inaccuracies caused by cross-sensitivity

Cross-sensitivity may cause several types of inaccurate reading in electrochemical gas detectors. These can be positive (indicating the presence of a gas even though it isn’t actually there, or indicating a level of that gas above its true value), negative (a reduced response to the target gas, suggesting that it is absent when it is actually present, or a reading that suggests there is a lower concentration of the target gas than there is), or the interfering gas can cause inhibition.

Inhibition occurs when the sensor simply fails to register the target gas when it is exposed to the target gas and the inhibitor together, or the inhibitor causes the sensor to stop registering the target gas for some time (which may be hours or even days) after exposure to the inhibitor.

Here are some examples of each error type:

Positive response error: a CO sensor has a positive response to H₂ at a rate of 60%. Thus, when the sensor detecting CO sees 200ppm of H₂ it indicates 60% of 200ppm (around 120ppm).
Negative response error: an SO₂ sensor has a –120% response to NO₂. So, if it sees 5ppm of NO₂ at the same time as 5ppm of SO₂, the reading is reduced by 6ppm, which (depending on the type of sensor involved) gives a 0ppm reading or negative value.
Inhibition: SO₂ sensors may be inhibited by NH₃, and take many hours to recover and respond to SO₂

All of these errors can have adverse effects. Clearly, danger arises when toxic gas is present and the sensor does not read correctly. But even when cross-sensitivity causes an over-reading or false positive, time and resources can be wasted by needless evacuations, ventilation and other unscheduled downtime.

Some manufacturers publish cross-sensitivity data and charts, and these can give some indication of how cross-sensitivities may influence readings in those products. However, it is important not to rely on these too heavily: there can be huge differences between electrochemical sensors, manufacturers may change their sensor designs and specifications at short notice, and scientific understanding is constantly evolving. So, it is a good idea to maintain dialogue with the manufacturer’s technical support team, who will be aware of the latest information and best placed to advise on a particular sensor. It is also sensible to ensure that any staff involved in gas detection are aware of the nature of cross-sensitivity and interference, and alert to its likely effects.

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