Understanding Both the PID Detector, the Application and the Limitations
PID Detectors are commonly used to monitor VOC’s (Volatile Organic Compounds). Many gases and vapours fall under the VOC banner and IGD’s PID’s can monitor for over 700 VOC gas species. This makes a PID an ideal first responder for VOC leaks even though the PID cannot directly determine the gas type detected. – See here to learn more about VOC gases.
For example, in a chemical plant where both Propylene and Acetone are present, leaks from either will be detected by a PID detector. In both cases the PID will report a ppm level leak detection. The PID however can’t determine if the leak detected is Acetone or Propylene. For this reason, the PID is a first responder for leak detection. Neither gas should be present in the atmosphere and both have occupational exposure limits. The PID can identify a leak has occurred, however pinpointing the source would then need to be undertaken by competent persons.
Deploying PID’s as fixed gas leak detectors can be undertaken as part of a sites risk mitigation strategy.
When doing so several factors need to be considered:
1. PID’s are first responders in that they are not specific to one gas but respond to many. If a specific gas detector is available for the target gas then this would usually be the more appropriate choice. For example, PID’s can detect Hydrogen Sulphide but specific Hydrogen Sulphide detectors are readily available and would be a better choice than fitting a PID for this application.
2. PID’s respond to a whole host of VOC’s. That needs to be considered to ensure false alarms or alarms to VOC’s you have not considered that exist in the area of application, don’t cause detection problems. For example, correctly sited PID detectors in a factory producing Cyanoacrylates can give excellent results to protect workers from emissions; ensuring processes are secure and well ventilated. However, placing the same detectors onto a vehicle production line, to help protect workers using adhesives in the production, could lead to poor results. In this case the new vehicles coming down the line are emitting all sorts of VOC’s from new paintwork, waxes, oils, solvents etc. All these VOC’s will be detected along with any VOC emissions from adhesives being used at particular workstations. So in this application it would not be possible to just isolate VOC’s from the adhesives as the factory has a high potential VOC background.
3. PID’s use ultra-violet light to ionise the sample gas stream. Some gases and vapours can react photochemically and form compounds that can coat the internal surfaces of the PID causing reduced sensitivity or in some cases device failure. Phosphine is a good example of such a compound. Phosphine can be detected at low levels using PID’s making it a good first responder for occupational exposure levels. However, it will react photochemically producing what are thought to be phosphorous oxides which can coat internal surfaces affecting performance. At low levels this can be accounted for during calibration.
Where significant exposure may happen then the PID should be cleaned. Phosphine detection is a good example where there are alternative detector technologies but handling phosphine for calibration is less than desirable making the PID a potentially better alternative. However as can be seen, it is important to fully understand the application when making a detector choice.
4. PID’s can be adversely affected in dirty and humid applications or where other non-responsive gases are present. Humidity can introduce leakage currents or refract the UV light resulting in lower sensitivity. IGD PID’s use an industry unique electrode stack design. This ensures the common issues of humidity interference are negated. Plus our unique electrode stack design also minimises false readings where possible and extend PID sensor life by as much as 200% longer than current PID technology. Where other gases are present that don’t respond on a PID these also work to reduce sensitivity (quenching) as the UV lights energy is absorbed in collision with molecules other than the target gas (if UV photons collide with a gas, they can’t ionise then that photon’s energy is lost reducing the amount of UV photons available). So again, it is important to understand the application and the characteristics of the PID being considered.
Is a PID detector a Good Choice for your Leak Detection Application?
IGD are here to help with that answer and ensure you make the right choice. With over 100 years of dedicated gas detection manufacturing, combined with over two decades of PID/VOC detection, we are the world’s experts in VOC detection. PID’s may be the correct choice but if an Infra-Red, Electrochemical, Catalytic or Semiconductor based detector offers a better solution then IGD can advise accordingly as we manufacture all these types making us uniquely placed to help you make your sensor choice. Our projects teams will be able to assist with this and help with choosing the right sensor technology for your application, after all each application is unique.
If a PID is the right choice for your application, then there are several types available to meet the exact needs of your application. See below the different options we manufacture and can provide
Fixed Diffusion based PID detectors
Our fixed diffusion PID detectors are available in safe area (non-ATEX), ATEX/IECEx. Diffusion based detectors allow gas to naturally migrate into the sensor for measurement. Detectors can either work in ‘stand-alone’ operation or by using IGD’s addressable systems, which allows them to be can be part of a wider detection network. Addressable systems have a large number of benefits that out-way the use of older standalone detectors. This includes them being IoT enabled, live digital signals, 70% cost saving on installation and 80% more capability per detector.
Sampling PID Detectors
As with the diffusion-based version, samplers are available either as ATEX or safe area versions. Samplers are a good choice in a number of applications:
- Clean rooms where a standard fixed detector acts as a ‘bug’ or dirt trap. Samplers require only a bulkhead fitting for the sample point minimising the impact in a clean room.
- Difficult to access areas benefit from samplers. The sampler can be in an easy to locate at a convenient point for access and tubed off to the location required. That point can be a sump, high level point etc that would otherwise be difficult to monitor and service.
IGD’s PID samplers offer additional benefits. PID Samplers can be configured to automatically self-zero at pre-determined intervals by drawing a scrubbed ‘clean’ air sample across the detector. This extends service intervals and provides excellent zero stability. PID samplers can operate addressable as part of a deployed IGD detection system.
Pictured: TOC-750S aspirated gas detector for remote sampling.
Portable PID Detectors
Where it is practical to fit fixed gas detection then this should always be undertaken as part of any gas risk mitigation strategy. In some cases, this is not practical. For example, confined entry for inspection into fuel tanks or down sewer systems are not places where fixed gas detection would be employed. In these cases, portable detectors are available for personal protection. In the case of the PID, a portable version may also be used to pinpoint the source of a VOC emission picked up on a fixed detector system or to provide personal protection in confined spaces. At IGD we offer a variety of portable PID gas detectors to fit the requirements of your sites. Please see below some of our options:
VOC-CHUM
The VOC-CHUM is a non-ATEX cost effective, VOC detector. It is designed for personal protection in non-ATEX environments such as medical, pharmaceutical and laboratories. The VOC-CHUM is simple to use and has a ergonomic design. This ensures our portable VOC monitor is the ideal cost effective solution for non-ATEX environments. Suitable for many applications including personal safety, government health, security and environmental agencies, pharmaceuticals, clean rooms and laboratories.
NEO PID – World Leading Portable VOC Detector.
The PID NEO is one of the most advanced portable VOC gas detectors available. Able to detect down to parts per billion levels (ppb) and up to 15,000 parts per million (ppm) levels. This makes it the ideal choice for a portable VOC gas detector, for pinpointing VOC leaks, investigating chemical spills, arson investigation, Benzene detection or ground gas works.
The NEO offers several models from the most sensitive 1ppb to a higher range 15,000ppm. This makes it the most versatile portable VOC gas detector on the market and suitable for a wide range of applications. The unique PID design ensures that the NEO provides outstanding sensitivity, stability and reproducibility. The three key qualities you need for VOC detection. It also includes real-time data monitoring, 3 point calibration, built in cross factor list and easily replaceable PID lamp. You can learn more about the NEO PID product page here and also book a demo visit.
Multi Gas Portable with VOC Detection.
Where VOC gases and multiple other gases are required to be detected in a portable format, such as confined space entry, then you will require a multi gas portable monitor. The POLI is the ideal solution to this, boasting the largest sensor configuration options on the market. The POLI can be supplied with a pump to allow for pre-entry and is packed full of outstanding features including man down alarms and pre-calibrated plug & play sensors. You check out the product page here.
Contact the Experts in VOC Detection Today.
There are many applications for portable VOC detection. PID’s from IGD offer excellent VOC detection for a wide range of applications. IGD can help provide advice to help you make the right choice; to meet the application and expected risk ensuring the best possible solution. Email us today or call us on +44(0)161 483 1415 for any help or product requirements.
