Keeping tabs on gas

We hear from Becca Dodds of Analox Sensor Technology on the importance of paying attention to gas monitoring in laboratories Atmosphere and process monitoring is an established procedure in laboratories around the world, but when one a developer of gas detection solutions reports a 50% increase in sales in the last 12 months it is an opportunity to ask if something has changed. An additional indication of the increased importance put on gas detection systems in laboratories is the inclusion of a new oxygen depletion monitor in the shortlist for the S-Lab Awards. Becca Dodds of Analox Sensor Technology says: “We believe the increase in sales is due to a number of factors, such as raised awareness of the dangers of inert gas, better and more accessible safety monitors, and changes in trends.  Labs are not only found in research centres and education facilities any more.  Labs are everywhere, even in our kitchens with the growing trend of using liquid nitrogen and dry ice in molecular gastronomy. There has also been a recent change in legislation in one country, but this growth has been global and it is important to delve into the reasons why.” Incidences involving speciality gases can lead to injuries or even fatalities, making detection vitally important as these gases are now used in a myriad of different ways. Carrier gases in laboratory processes, in cryogenics, in tissue preservation, in silicon growth atmospheric protection, as coolant for superconductors such as MRI scanners…the list goes on. These gases are used in a variety of laboratories, from industry to hospitals, from agriculture to food research, as well as in universities and schools. The gases which are being used include inert gases such as argon, liquid nitrogen and helium, which can cause oxygen depletion within a confined space. Carbon dioxide, a toxic gas undetectable by humans, is also widely used, and some laboratories would have the need to monitor for flammable gases or volatile organic compounds. Inert gases, such as argon, liquid nitrogen, and helium, can lead to oxygen (O₂) depletion should they leak undetected into a confined space. The normal level of O₂ in the atmosphere is approximately 21%. Only a couple of percentage points below this can begin to adversely affect the human body, with symptoms that may not immediately be attributed to O₂ depletion. It is important staff are made aware of a potential risk immediately as even a small spillage of liquid can quickly turn into a mass of deadly gas. For this reason, gas monitors are key to the safety of personnel.

• Between 21 and 14% of oxygen, a person is likely to have an increased pulse rate, and feel generally tired.
• Between 14 and 11%, physical movement and intellectual performance becomes difficult.
• Between 11 and 8%, a person is likely to suffer headaches, dizziness and fainting after a relatively short period of time.
• Between 8 and 6%, fainting is expected within a few minutes with resuscitation possible if carried out immediately.
• Between 6 and 0%, fainting would be expected almost immediately, resulting in severe brain damage or potentially death.

To ensure complete safety in the event of O₂ depletion, the ideal monitoring system should be programmed with two alarm points. Dodds’ recommendation is a first trigger point at 19.5%, which will alert staff that there is a problem that needs to be identified and corrected. Then a second trigger point at 18% is the notification that the space needs to be evacuated for the safety of all working there. O₂ monitors should be positioned at normal working head height. Carbon dioxide (CO₂) is now used widely, and not only in laboratories. This toxic gas is undetectable by humans until the concentration reaches potentially dangerous levels. Once again, the effects of CO₂ enrichment on the body, especially the early symptoms, could easily be blamed on other factors.

• At 1%, a person would have a slight, but un-noticeable increase in the breathing rate.
• At 2%, breathing becomes deeper, and the breathing rate is likely to be approximately 50% faster than normal. Prolonged exposure at this level is likely to cause a headache and/or a feeling of exhaustion.
• At 3%, breathing becomes laboured, speeding to double the normal rate.  Hearing can be impaired, and headaches are likely. A person’s blood pressure and pulse rate will both be increased.
• At 4 to 5%, 30 minutes exposure time is likely to lead to apparent signs of intoxication, as well as a slight choking feeling.
• At 5 to 10%, a pungent smell is noticeable, such as the smell of carbonated water. At these levels, breathing is very laboured, leading to physical exhaustion. As well as headaches, a person will experience visual disturbance, ringing in the ears, and confusion. A person is likely to lose consciousness within minutes.
• With levels higher than 10%, loss of consciousness comes more quickly, and there is a risk of death from respiratory failure. As the concentration increases, so the hazard to life increases even if there is no oxygen depletion.

The UK has assigned a workplace exposure limit of 5,000 ppm (0.5%) over eight hours, and 15,000 ppm (1.5%) for 10 minutes. These limits are in line with international safety limits, and CO₂ monitors would normally have alarms set to trigger at both of these concentrations. CO₂ monitors should be positioned 450mm above the floor level, as the gas is heavier than air. Flammable gases are a potential risk not only because they could lead to fire, but also because they can lead to poisoning, asphyxiation and potentially could cause explosions. Flammable gases, including methane, propane, hydrogen, cyanide and butane, are detected by pellistor (catalytic bead) sensors. The use of electrochemical galvanic fuel cells in sensors enables the effective monitoring of toxic gases. These gases include carbon monoxide, chlorine, fluorine, hydrogen, nitrogen dioxide, nitric oxide, ozone, phosphine, sulphur dioxide and more. Electrochemical sensors are also used to detect volatile organic compounds (VOCs) which are any organic compound with an initial boiling point less than or equal to 250°C at standard atmospheric pressure. VOCs are found in oils, solvents, paints and similar, and have the potential to cause damage to visual and audible senses, and to cause long term health problems. It is possible that increased awareness of health and safety in the work place, and better understanding of the hazards associated with speciality gases, has led to the increase in installation of gas monitoring systems. In the UK, the Confined Spaces Regulations 1997 apply where assessment identifies risk of serious injury from work within the confined space. Confined space regulations for laboratories require a suitable monitoring and alarm system to be in place where the gases are stored and used. There has recently been a change in UK law which states that disposable bottles of 24-100% O₂ cannot be shipped. Such bottles have previously been supplied for use in the calibration of monitors. In response to this restriction, some suppliers have modified their units so that they can now be calibrated using a synthetic air. Technological developments have improved the performance of gas analysis systems so that reliably accurate monitoring systems which can work in even the most inhospitable of environments – including high or low temperatures, or hypobaric and hyperbaric condition – can now be achieved. Infra-red sensing to detect levels of CO₂ in the atmosphere is now an established method. When introduced, it enabled more cost-effective monitoring systems to be produced, expanding the markets for such gas analysis equipment. This method has now been in use for more than 30 years. In recent years, further developments have allowed the introduction of portable units which are ideal for anyone delivering speciality gases, and those whose jobs require them to enter unmonitored confined spaces. Combined gas analysis with movement monitoring has given portable units a ‘man down’ alarm to ensure those nearby are quickly aware that someone may be unconscious. Maintenance of such monitors is also important and it falls to the user to ensure correct calibration, and sensor instalment. Dodds adds: “When you’re at work you want to be focused on what you’re employed to do, what you do best. You don’t want to spend your time calibrating and testing the gas analysis equipment and replacing sensors. Technology continues to advance, which has made the units easier to maintain. There are currently oxygen sensors available with a potential life span of ten years, as well as monitoring units that require calibrating once every 18 months. Accidental or incorrect calibration can leave staff at risk so it is important that these safety devices are user maintainable, and quick and easy to calibrate.” The increased importance put on gas detection systems in laboratories is highlighted by the inclusion of a new O₂ depletion monitor in the shortlist for the S-Lab Awards. Analox Sensor Technology’s O2NE+ is competing for the title of Best New Product against a range of very different newly-launched products. Within a laboratory there are a number of factors which could lead staff to continue with their work oblivious to a gas leak which could cause them harm. Dodds says: “Most of these dangerous gases are undetectable by human senses. Additionally, in some laboratories, staff need to wear masks and goggles as part of their PPE which can cause a delay in the detection of a problem. It is therefore vital that an alarm system is installed in areas at risk.” Clearly, the need for gas analysis is understood and appreciated in the majority of laboratories. Management and staff want an easy solution, one that requires very little of their attention to maintain their safety and well-being while they concentrate on the purpose of their work. Whilst accuracy is of the utmost importance, cost-effectiveness is also valid. Another factor to take into consideration is whether the monitoring system can be expanded should work areas be enlarged. Dodds concluded: “Spend the time initially investigating the right monitoring system for your operation. Assess the situation periodically to ensure all changes have been catered for. It doesn’t need to be a complicated process to ensure that your staff are protected, and that any change in the atmosphere will be quickly detected so that actions can be taken to make the area safe long before anyone comes to any harm. “The gas analysis providers must be close to their clients, to those using the products, must work closely with them. By listening to and learning from those who are installing and using atmosphere monitoring systems in laboratories, the solutions will continue to improve, always with the aim of meeting the needs of the client, never mind how challenging those needs are.”