VOCs in the Workplace and the Advantages of VOC Detectors
What are VOCs and Why are They Dangerous?
Volatile organic compounds (VOCs) are a group of carbon-based chemicals that have a high vapour pressure. Generally, any organic compound with an initial boiling point that is equal to or less than 250°C measured at standard atmospheric pressure of 1.013 kPA is considered a volatile organic compound (VOC). They are used as solvents in many industries and emitted as gases by countless household products including paints, cleaning supplies, furnishings, adhesives and plenty more. Common VOCs include benzene, ethylene glycol, formaldehyde, methylene chloride, tetrachloroethylene and xylene, with there being plenty more chemicals classified as VOCs.
Exposure to VOCs are a safety concern in many industries, and dangers can vary according to the exact chemicals, however plenty of VOCs are known to cause headaches, dizziness and irritation in the eyes or throat, and can also be extremely toxic and even carcinogenic. Effects can potentially be immediate in high concentrations, however typically symptoms won’t be experienced until months or years have passed and will develop as a chronic illness from repeated exposure to low concentrations over an extended duration. This can result in damage to the liver, kidney and the central nervous system among other areas. If the concentration is high enough to displace oxygen, death also becomes a potential risk. Additionally, VOCs can pose an environmental risk by reacting with other chemicals to create secondary pollutants such as ozone and other harmful substances. This can harm both animal and plant life, bleaching forests and crops.
VOC Monitoring Health and Safety Regulations in the Workplace
Under Section 17 of the WHS Act, businesses are required to eliminate or reduce health and safety risks as far as is reasonably practicable. They are also required to monitor the workplace conditions to prevent injury and illness as far as is reasonably practicable under Section 19. Workplaces will generally implement control measures to reduce or eliminate risks, which for VOCs can include methods such as ventilation, air filtration, carbon adsorption and thermal oxidation. Controls will differ depending on whether the intention is simply to remove the VOCs or to collect them for reuse.
In addition to these broader requirements, Safe Work Australia also imposes workplace exposure standards (WES) to ensure harmful levels of specific airborne contaminants are not exceeded in the workplace. There are three forms of WES;
8-hour time-weighted average (TWA) – The maximum average concentration allowed over an eight-hour working day for a five-day week.
Short term exposure limit (STEL) – The maximum time-weighted average over a 15-minute period that must not be exceeded. Exposure to this level must not be repeated more than fours time a day, with 60 minute intervals. This is in addition to the TWA.
Peak limitation – The maximum airborne concentration over the shortest analytically practicable period below 15 minutes.
Types of VOC Detectors and Their Features and Applications
What Type of Sensor is Best Suited to VOC Detection?
VOC detection is naturally extremely important in many industries given the dangers posed by these gases and the regulations that have therefore been enforced. In the past, it was common to measure VOCs according to their lower explosive limits (LEL), the level at which they become flammable. This, however, was found to be insufficient, with many compounds such as diesel and jet fuel being toxic before reaching flammable levels. Moreso than the risk of explosion, workers could develop serious health conditions including respiratory problems after extended and repeated exposure.
In response to this, photoionisation detectors (PIDs) have gained popularity due to their ability to detect a wider range of VOCs at lower levels than any other method of detection. Their incredible sensitivity allows them to detect hazardous chemicals at the ppb level, making them suitable for a wide range of applications. This, however, does not mean that LEL sensors have been replaced. Instead, it is preferrable to have both LEL and PID sensor capability together in a single instrument as complementary technologies.
Other options for VOC detection include electrochemical sensors and metal oxide sensors, both of which are compact and low cost. These sensors, however, have more drawbacks than PIDs, with electrochemical sensors only being able to target one compound and being slower, and metal oxide sensors being less sensitive and responsive to some inorganic substances. These types of sensors are hence only preferrable to PIDs in very specific situations, but similarly to LEL sensors, can be incorporated into an instrument alongside a photoionisation (PID) sensor to cover more applications. Given the high sensitivity, stability and response time of PIDs, they are generally accepted as the best sensor for detecting VOCs.
Advantages and Disadvantages of PID Sensors for VOC Detection
PIDs are considered the most suitable sensors for detecting VOCs due to their high sensitivity and capacity for detecting a wide range of chemicals at lower levels than other sensors. On the other hand, they can also have some limitations.
PIDs have traditionally been known to suffer from humidity issues, resulting in false alarms and creating issues when calibrating the device in, for example, an air conditioned indoor environment before using the PID in an outdoor environment. Previously, some devices used desiccants or humidity detectors in attempt to mitigate this issue, however this was not an effective solution. As technology has progressed with time, patented Fence Electrode Technology has been developed to allow humidity to pass through the device directly, limiting its interference for reliable, uninterrupted measurements and allowing PIDs such as the Ion Science Tiger XT VOC Detector to detect VOCs with precision. This also means that instruments using this technology can deliver faster response times with rapid clear-downs, making them suitable for fast evolving situations where worker safety is reliant on quick and precise readings.
In addition to humidity, temperature can also affect the sensitivity of PIDs to a degree. Some instruments use an ASIC chip to counter this, allowing the PID to run stably and from -40°C to 65°C. Unlike traditional portable gas detectors, PIDs are also unable to identify specific gases or the concentration of different compounds present. They will instead give a single, cumulative reading that can be used as an indication of an overall danger level or in tasks such as leak detection.
Common Applications Where PID Monitors Are Used to Detect VOCs
With new advancements in PID technology, decrease in cost of ownership and ease of maintenance, the use of VOC detectors has become much more commonplace across a variety of industries. Industries in which the use of PIDs is suited to include oil and gas, petrochemical, chemical plants, wastewater, emergency response and environmental monitoring. A lot of these environments have high humidity or contamination, meaning that PIDs with humidity resistant and anti-contamination designs such as the Tiger XT Series VOC detectors are ideally suited. This includes the Ion Science Tiger XT Select Benzene Detector, which is especially suitable when benzene in particular is an issue, such as in the oil and gas industry given that PIDs cannot normally differentiate between VOCs.
Portable and robust with IP65 Ingress Rating Protection, the Tiger XT Series have also been designed to withstand harsh environments and is ideal for use in surveying applications such as emergency response and a variety of industrial applications with its handheld design. In these applications, the fast response time of the device is also extremely beneficial and can also help to indicate the direction of any leaks according to the concentration of VOCs.
Alternatively, personal VOC detectors such as the Cub Personal PID Gas Monitor can be worn on the body of the worker and are more suitable for monitoring exposure while working in a VOC prone environment and alerting workers when a dangerous level of VOCs are reached. PIDs can be used anywhere where VOCs are present and as a result, the applicable industries can be quite broad. From measuring VOC concentration when cleaning a contaminated site to the detection of vinyl chloride which is used to produce PVC, the list of industries in which PIDs can be used is endless.
Aside from VOC exclusive instruments, personal multi-gas detectors with PID VOC sensors can also be helpful in particular circumstances, particularly occupational hygienists who are concerned with health risks as opposed to just safety. Instruments such as the Ventis Pro5 Multi Gas Monitor designed to monitor multiple gases while also being equipped with PID sensing capabilities, making them especially suitable for these applications. The Industrial Scientific Ventis Pro5 also comes with the added benefit of live monitoring via the iNet platform and variety in connectivity solutions allowing for a truly connected VOC detection program.
It can be difficult understanding the suitability of different VOC detectors to a specific application given the variety of features and capabilities of each instrument. PIDs are available at Air-Met Scientific for sale or rental.
