Gas Hazards in Wastewater

Water is vital to our daily lives, both for personal and domestic use and industrial/commercial applications making water sites both numerous and widespread. Despite the quantity and location of water sites, only two environments predominate, and these are quite specific. They are clean water and wastewater. This blog details gas risks encountered at wastewater sites and how they may be mitigated. 

The wastewater industry is always wet, with temperatures between 4 and 20oc near the water and rarely far from that limited temperature range even away from the immediate location of the wastewater. 90%+ relative humidity, 12 +/- 8oc, atmospheric pressure, with multiple toxic and flammable gas hazards and the risk of oxygen depletion. Gas detectors must be chosen to suit the specific environment in which they operate, and whilst high humidity is generally challenging to all instrumentation, the constant pressure, moderate temperatures and narrow temperature range is a far greater benefit to safety instrumentation. 

Gas Hazards  

The main gases of concern in wastewater treatment plants are: 

  • Methane 
  • Hydrogen sulphide 
  • Carbon dioxide  
  • Reduced levels of oxygen 

Hydrogen sulphide, methane and carbon dioxide are the by-products of the decomposition of organic materials that exist in the waste flows feeding the plant. The build-up of these gases may lead to the lack of oxygen, or in some cases, explosion when coupled with a source of ignition. 

Hydrogen sulphide (H2S)

Hydrogen sulphide is a common product of the biodegradation of organic matter; pockets of H2S can collect in rotting vegetation, or sewage itself, and be released when disturbed. Workers in sewerage and wastewater plants and pipework can be overcome by H2S, with fatal consequences. Its high toxicity is the main danger of H2S. Prolonged exposure to 2-5 parts per million (ppm) H2S can cause nausea and headaches and bring tears to the eyes. H2S is an anaesthetic, hence at 20ppm, symptoms include fatigue, headaches, irritability, dizziness, temporary loss of the sense of smell and impaired memory. Severity of symptoms increase with concentration as nerves shut down, through coughing, conjunctivitis, collapse and rapid unconsciousness. Exposure at higher levels can result in rapid knock down and death. Prolonged exposure to low levels of H2S may cause chronic illness or can also kill. Because of this, many gas monitors will have both instantaneous and TWA (Time-Weighted Average) alerts. 

Methane (CH4)

Methane is a colourless, highly flammable gas that is the primary component of natural gas, also referred to as biogas. It can be stored and/or transported under pressure as a liquid-gas. CH4 is a greenhouse gas that is also encountered in normal atmospheric conditions at a rate of approximately 2 parts per million (ppm). High exposure can lead to slurred speech, vision problems and memory loss. 

Oxygen (O2)

The normal concentration of oxygen in the atmosphere is approximately 20.9% volume. In the absence of adequate ventilation, the level of oxygen can be reduced surprisingly quickly by breathing and combustion processes. Olevels may also be depleted due to dilution by other gases such as carbon dioxide (also a toxic gas), nitrogen or helium, and chemical absorption by corrosion processes and similar reactions. Oxygen sensors should be used in environments where any of these potential risks exist. When locating oxygen sensors, consideration needs to be given to the density of the diluting gas and the “breathing” zone (nose level). 

Safety Considerations 

Risk assessment

Risk assessment is critical, as you need to be aware of the environment that you are entering and thus working in. Therefore, understanding the applications and identifying the risks regarding all safety aspects. Focusing on gas monitoring, as part of the risk assessment, you need to be clear on what gases may be present. 

Fit for purpose

There is a variety of applications within the water treatment process, giving the need to monitor multiple gases, including carbon dioxide, hydrogen sulphide, chlorine, methane, oxygen, ozone and chlorine dioxide. Gas detectors are available for single or multiple gas monitoring, making them practical for different applications as well as making sure that, if conditions change (such as sludge is stirred up, causing a sudden increase in hydrogen sulphide and flammable gas levels), the worker is still protected. 

Legislation  

European Commission Directive 2017/164 issued in January 2017, established a new list of indicative occupational exposure limit values (IOELVs). IOELV are health-based, non-binding values, derived from the most recent scientific data available and considering the availability of reliable measurement techniques. The list includes carbon monoxide, nitrogen monoxide, nitrogen dioxide, sulphur dioxide, hydrogen cyanide, manganese, diacetyl and many other chemicals. The list is based on Council Directive 98/24/EC that considers the protection of the health and safety of workers from the risks related to chemical agents in the workplace. For any chemical agent for which an IOELV has been set at Union level, Member States are required to establish a national occupational exposure limit value. They also are required to take into account the Union limit value, determining the nature of the national limit value in accordance with national legislation and practice. Member States will be able to benefit from a transitional period ending at the latest on 21 August 2023. 

The Health and Safety Executive (HSE) state that each year several workers will suffer from at least one episode of work-related illness. Although, most illnesses are relatively mild cases of gastroenteritis, there is also a risk for potentially fatal diseases, such as leptospirosis (Weil’s disease) and hepatitis. Even though these are reported to the HSE, there could be significant under-reporting as there is often failure to recognise the link between illness and work. 

Our solutions  

Elimination of these gas hazards is virtually impossible, so permanent workers and contractors must depend on reliable gas detection equipment to protect them. Gas detection can be provided in both fixed and portable forms. Our portable gas detectors protect against a wide range of gas hazards, these include T4x, Clip SGD, Gasman, Tetra 3, Gas-Pro, T4 and Detective+. Our fixed gas detectors are used where reliability, dependability and lack of false alarms are instrumental to efficient and effective gas detection, these include Xgard, Xgard Bright and IRmax. Combined with a variety of our fixed detectors, our gas detection control panels offer a flexible range of solutions that measure flammable, toxic and oxygen gases, report their presence and activate alarms or associated equipment, for the wastewater industry our panels include Gasmaster.   

To find out more on the gas hazards in wastewater visit our industry page for more information. 

Are there dangers of gas in telecommunications? 

The telecommunication industry contains includes cable providers, internet service providers, satellite providers and telephone providers and confined spaces. Even simple above ground termination boxes may contain gas hazards generated from the cable runs underground. Gases such as methane, carbon dioxide and hydrogen sulphide can run through cable trunking accumulating in termination boxes and manifesting as hazards when the termination box is opened.

The risk of danger occurs when a worker is sent to carry out tasks involving opening up of enclosed volumes that may not have been accessed for a period of time. All telecommunications companies have these in abundance.

What are the Dangers?

Those working in the telecommunications industry are at risk from a variety of gaseous dangers, many of which could cause harm to their health and safety. Though less obvious, these risks should be taken as seriously as falls from heights or electrocution, and they require a similar level of training. A worker must not climb to an elevated position without a harness, similarly they shouldn’t be accessing confined spaces without appropriate confined space training. Awareness of the dangers present and minimising the risks that could lead to adverse effects is a well-known safety principle. Training and proper PPE can help protect workers from these hazards.

Gas Hazards and Risks

As there are many confined spaces in the telecommunication industry workers are at risk from the presence of hazardous and toxic gases there. Hazardous gases can also be linked to seemingly simple above-ground termination boxes. Gases such as methane, carbon dioxide and hydrogen sulphide sometimes travel through the cable trunking, and therefore, when the termination box is opened, a build-up of these gases can be released.

Enclosed or partially enclosed spaces with high levels of methane in the air reduce the amount of oxygen available to breathe and therefore can cause mood changes, speech and vision problems, memory loss, nausea, sickness, facial flushing and headaches. In more severe cases and prolonged exposure, there may be changes in breathing and heart rate, balance problems, numbness, and unconsciousness. There is also a risk of fire as methane is highly flammable.

Carbon monoxide (CO) consumption also poses serious health issues to workers, with those ingesting the toxic substance facing flu-like symptoms, chest pain, confusion, fainting arrhythmias, seizures, or even worse health effects for high or long lasting exposures. Hydrogen sulphide (H2S) poisoning causes similar issues, as well as delirium, tremors, convulsions, and skin and eye irritation. Carbon dioxide is an asphyxiant gas that can displace oxygen and hance dizziness.

Our solution

Gas detection can be provided in both fixed and portable forms. Our portable gas detectors protect against a wide range of gas hazards, these include Tetra 3 and T4. Our fixed gas detectors are used where reliability, dependability and lack of false alarms are instrumental to efficient and effective gas detection, these include Xgard and Xgard Bright. Combined with a variety of our fixed detectors, our gas detection control panels offer a flexible range of solutions which are able to measure flammable, toxic and oxygen gases, report their presence and activate alarms or associated equipment, for the telecommunication industry our panels include Gasmaster.

To find out more on the dangers of gas hazards in telecommunication visit our industry page for more information.

Transportation and Key Gas Challenges 

The transportation sector is one of the largest industries in the world, spanning a variety of applications. The sector offers services concerned with the movement of people and cargo of all types, across air freight and logistics, airlines and airport services, road and rail, transportation infrastructure, trucking, highways, rail tracks, and marine ports and services. 

Gas hazards during transportation  

The transport of dangerous goods is regulated in order to prevent, accidents involving people or property, damage to the environment. There a numerous gas hazards including the transportation of hazardous material, air conditioning emissions, cabin combustion and hangar leaks.  

The transportation of hazardous materials poses a risk to those involved. There are nine classification areas specified by the United Nations (UN) including explosives, gases, flammable liquids and solids, oxidising substances, toxic substances, radioactive materials, corrosive substances and miscellaneous goods. With the risk of an accident occurring being more likely when transporting these materials. Although the biggest cause for concern within the industry being the transportation of non-flammable non-toxic gas is asphyxiation. As a slow leak in a storage container can drain all of the oxygen in the air and cause the individuals in the environment to suffocate. 

Leaks within aircraft hangars and fuel storage areas of highly explosive aviation fuel is an area that must be monitored to prevent fires, equipment damage, and at the worst fatalities. It is essential to choose a suitable gas detection solution that focuses on the aircraft rather than the aircraft hangar, avoids false alarms, and can monitor large areas. 

Not only is it the external environment that faces gas risks in transportation, those working in the sector also face similar challenges. Air conditioning emissions poses a gas hazard threat due to the burning of fossil fuels leading to a subsequent emission of carbon monoxide (CO). high levels of CO in a confined area such as a vehicle cabin, of more than the normal level (30ppm) or an oxygen level below normal (19%) can result in dizziness, feeling and being sick, tiredness and confusion, stomach pain, shortness of breath and difficulty breathing. Therefore, proper ventilation in these spaces with the assistance of a gas detector is paramount to ensuring the safe of those working in the transportation industry.  

Similarly, in the air sector cabin combustion and fuselage fires, in the central portion of an airplane, poses a real threat. Although flame retardant materials are applied, if a fire does start the cabin’s trim and fittings can still generate toxic gases and vapours that could be more dangerous than the fire itself. Inhalation of harmful gases caused by a fire in these environments tend to be the main direct cause of fatalities.  

Transportation Standards and Certifications 

Each mode of transport, (road, rail, air, sea and inland waterway) has its own regulations but they are generally harmonized with the United Nations Economic Commission for Europe (UNECE). The Hazardous Materials Transportation Act (HMTA), enacted in the USA in 1975, states that regardless of the type of transportation, any company whose goods fall into one of the nine categories specified as hazardous by the UN, must comply with the regulations or risk fines and penalties. 

Those working in the transport sector in the UK must comply with the requirements laid out in the UN Model Regulations which assigns each dangerous substance or article a specific class that correlates how dangerous it is. It does this via the packing group (PG) classification, according to PG I, PG II or PG III. 

From an European standpoint the International Carriage of Dangerous Goods by Road (ADR) governs the regulations on how to classify, pack, label and certify dangerous goods. It also comprises vehicle and tank requirements and other operational requirements. The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations (2009) also is relevant in England, Wales and Scotland. 

Other relevant regulations include the International Carriage of Dangerous Goods by Inland Navigation (ADN), the International Maritime Dangerous Goods (IMDG) and The International Civil Aviation Organization’s (ICAO) Technical Instruction 

Our solution 

Gas detection can be provided in both fixed and portable forms. Our portable gas detectors protect against a wide range of gas hazards, these include T4x, Clip SGD, Gasman, Tetra 3, Gas-pro, T4. Our fixed gas detectors are used where reliability, dependability and lack of false alarms are instrumental to efficient and effective gas detection, these include Xgard, Xgard Bright, IRmax. Combined with a variety of our fixed detectors, our gas detection control panels offer a flexible range of solutions which are able to measure flammable, toxic and oxygen gases, report their presence and activate alarms or associated equipment, for the transportation industry our panels include Gasmaster and Vortex 

To find out more on the dangers of gas hazards in transportation visit our industry page for more information.  

The Benefits of MPS Sensors 

Developed by NevadaNano, Molecular Property Spectrometer™ (MPS™) sensors represent the new generation of flammable gas detectors. MPS™ can quickly detect over 15 characterised flammable gases at once. Until recently, anyone who needed to monitor flammable gases had to select either a traditional flammable gas detector containing a pellistor sensor calibrated for a specific gas, or containing an infra-red (IR) sensor which also varies in output according to the flammable gas being measured, and hence needs to be calibrated for each gas. While these remain beneficial solutions, they are not always ideal. For example, both sensor types require regular calibration and the catalytic pellistor sensors also need frequent bump testing to ensure they have not been damaged by contaminants (known as ‘sensor poisoning’ agents) or by harsh conditions. In some environments, sensors must frequently be changed, which is costly in terms of both money and downtime, or product availability. IR technology cannot detect hydrogen – which has no IR signature, and both IR and pellistor detectors sometimes incidentally detect other (i.e., non-calibrated) gases, giving inaccurate readings that may trigger false alarms or concern operators. 

The MPS™ sensor delivers key features that provide real world tangible benefits to operator and hence workers. These include: 

No calibration  

When implementing a system containing a fixed head detector, it is common practice to service on a recommended schedule defined by manufacturer. This entails ongoing regular costs as well potentially disrupting production or process in order service or even gain access to detector or multiple detectors. There may also be a risk to personnel when detectors are mounted in particularly hazardous environments. Interaction with an MPS sensor is less stringent because there are no unrevealed failure modes, provided air is present. It would be wrong to say there is no calibration requirement. One factory calibration, followed by a gas test when commissioning is sufficient, because there is an internal automated calibration being performed every 2 seconds throughout the working life of the sensor. What is really meant is – no customer calibration. 

The Xgard Bright with MPS™ sensor technology does not require calibration. This in turn reduces the interaction with the detector resulting in a lower total cost of ownership over the sensor life cycle and reduced risk to personnel and production output to complete regular maintenance. It is still advisable to check the cleanliness of the gas detector from time to time, since gas can’t get through thick build ups of obstructive material and wouldn’t then reach the sensor. 

Multi species gas – ‘True LEL’™  

Many industries and applications use or have as a by-product multiple gases within the same environment. This can be challenging for traditional sensor technology which can detect only a single gas that they were calibrated for at the correct level and can result in inaccurate reading and even false alarms which can halt process or production if another flammable gas type is present. The lack of response or over response frequently faced in multi gas environments can be frustrating and counterproductive compromising safety of best user practices. The MPS™ sensor can accurately detect multiple gases at once and instantly identify gas type. Additionally, the MPS™ sensor has a on board environmental compensation and does not require an externally applied correctional factor. Inaccurate readings and false alarms are a thing of the past.  

No sensor poisoning  

In certain environments traditional sensor types can be under risk of poisoning. Extreme pressure, temperature, and humidity all have the potential to damage sensors whist environmental toxins and contaminants can ‘poison’ sensors, leading to severely compromised performance. Detectors in environments where poisons or inhibitors may be encountered, regular and frequent testing is the only way to ensure that performance is not being degraded. Sensor failure due to poisoning can be a costly experience. The technology in the MPS™ sensor is not affected by contaminates in the environment. Processes that have contaminates now have access to a solution that operates reliably with fail safe design to alert operator to offer a peace of mind for personnel and assets located in hazardous environment. Additionally, the MPS sensor is not harmed by elevated flammable gas concentrations, which may cause cracking in conventional catalytic sensor types for example. The MPS sensor carries on working. 

Hydrogen (H2)

The usage of Hydrogen in industrial processes is increasing as the focus to find a cleaner alternative to natural gas usage. Detection of Hydrogen is currently restricted to pellistor, metal oxide semiconductor, electrochemical and less accurate thermal conductivity sensor technology due to Infra-Red sensors inability to detect Hydrogen. When faced with challenges highlighted above in poisoning or false alarms, the current solution can leave operator with frequent bump testing and servicing in addition to false alarm challenges. The MPS™ sensor provides a far better solution for Hydrogen detection, removing the challenges faced with traditional sensor technology. A long-life, relatively fast responding hydrogen sensor that does not require calibration throughout the life cycle of the sensor, without the risk of poisoning or false alarms, can significantly save on total cost of ownership and reduces interaction with unit resulting in peace of mind and reduced risk for operators leveraging MPS™ technology. All of this is possible thanks to MPS™ technology, which is the biggest breakthrough in gas detection for several decades. The Gasman with MPS is hydrogen (H2) ready. A single MPS sensor accurately detects hydrogen and common hydrocarbons in a fail-safe, poison-resistant solution without recalibration.

For more on Crowcon, visit https://www.crowcon.com or for more on MPSTM visit https://www.crowcon.com/mpsinfixed/  

What causes Hydrocarbon Fires?  

Hydrocarbon fires are caused by fuels containing carbon being burned in oxygen or air. Most fuels contain significant levels of carbon, including paper, petrol, and methane – as examples of solid, liquid or gaseous fuels – hence hydrocarbon fires. 

For there to be an explosion risk there needs to be at least 4.4% methane in air or 1.7% propane, but for solvents as little as 0.8 to 1.0% of the air being displaced can be enough to create a fuel air mix that will explode violently on contact with any spark.

Dangers associated with hydrocarbon fires

Hydrocarbon fires are considered highly dangerous when compared to fires that have ignited as a result of simple combustibles, as these fires have the capacity to burn at a larger scale as well as also having the potential to trigger an explosion if the fluids released cannot be controlled or contained. Therefore, these fires pose a dangerous threat to anyone who works in a high-risk area, the dangers include energy related dangers such as burning, incineration of surrounding objects. This is a danger due to the ability that the fires can grow quickly, and that heat can be conducted, converted and radiated to new sources of fuel causing secondary fires. 

Toxic hazards may be present in combustion products, for example, carbon monoxide (CO), hydrogen cyanide (HCN), hydrochloric acid (HCL), nitrogen dioxide (NO2) and various polycyclic aromatic hydrocarbons (PAH) compounds are dangerous for those working in these environments. CO uses the oxygen that is used to transport the red blood cells around the body, at least temporarily, impairing the body’s ability to transport oxygen from our lungs to the cells that need it. HCN adds to this problem by inhibiting the enzyme that tells the red blood cells to let go of the oxygen they have where it is needed – further inhibiting the body’s ability to get the oxygen to the cells that need it. HCL is a generally an acidic compound that is created through overheated cables. This is harmful to the body if ingested as it affects the lining of the mouth, nose, throat, airways, eyes, and lungs. NO2 is created in high temperature combustion and that can cause damage to the human respiratory tract and increase a person’s vulnerability to and in some cases lead to asthma attacks. PAH’s affects the body over a longer period of time, with serve cases leading to cancers and other illnesses. 

We can look up the relevant health levels accepted as workplace safety limits for healthy workers within Europe and the permissible exposure limits for the United States. This gives us a 15-minute time weighted average concentration and an 8-hour time weighted average concentration. 

For the gases these are: 

Gas  STEL (15-minute TWA)  LTEL (8-hour TWA)  LTEL (8hr TWA) 
CO  100ppm  20ppm  50ppm 
NO2  1ppm  0.5ppm  5 Ceiling Limit 
HCL  1ppm  5ppm  5 Ceiling Limit 
HCN  0.9ppm  4.5ppm  10ppm 

The different concentrations represent the different gas risks, with lower numbers needed for more dangerous situations. Fortunately, the EU has worked it all out for us and turned it into their EH40 standard. 

Ways of protecting ourselves

We can take steps to ensure we do not suffer from exposure to fires or their unwanted combustion products. Firstly of course, we can adhere to all fire safety measures, as is the law. Secondly, we can take a pro-active approach and not let potential fuel sources accumulate. Lastly, we can detect and warn of the presence of combustion products using appropriate gas detection equipment. 

Crowcon product solutions

Crowcon provides a range of equipment capable of detecting fuels and the combustion products described above. Our PID products detect solids and liquid-based fuels once they are airborne, as either hydrocarbons on dust particles or solvent vapours. This equipment includes our GasPro portable. The gases can be detected by our Gasman single gas, T3 multi gas and Gas-Pro multi gas pumped portable products, and our Xgard, Xgard Bright and Xgard IQ fixed products – each of which has the capability of detecting all the gases mentioned.