VOC around? Find out.
Volatile organic compounds (VOCs) can be present in workplaces without being visible, making the right gas detection equipment critical when workers may be exposed to hazardous atmospheres.
A Photoionisation Detector (PID) provides rapid detection of a broad range of VOCs at very low concentrations. When incorporated into a multi-gas monitor, PID technology can provide VOC monitoring alongside common confined-space gases such as oxygen (Oâ‚‚), carbon monoxide (CO), hydrogen sulphide (Hâ‚‚S) and combustible gases (LEL).
What is a Photoionisation Detector (PID)?
A Photoionisation Detector is a type of gas sensor primarily used to detect volatile organic compounds (VOCs) and other ionisable gases.
Rather than waiting for a substance to reach combustible concentrations, a PID can detect many compounds at parts-per-million (ppm) or lower concentrations, depending on the instrument, lamp and target compound.
This makes PID monitoring particularly useful where the hazard is toxic exposure rather than simply flammability.
How does a PID gas detector work?
A PID uses an ultraviolet (UV) lamp to expose gas molecules entering the detector to high-energy photons.
If a compound’s ionisation energy is lower than the energy produced by the PID lamp, the molecule can be ionised. The resulting electrical current is measured by the instrument and converted into a concentration reading.
In simple terms:
Air enters the detector → UV light ionises detectable compounds → the detector measures the response → a VOC concentration is displayed.
What are VOCs?
Volatile organic compounds are carbon-containing chemicals that readily evaporate into the air.
Depending on the workplace, VOCs may be released from:
- Fuels and petroleum products
- Solvents and thinners
- Paints and coatings
- Adhesives and resins
- Cleaning chemicals
- Degreasers
- Contaminated soil
- Industrial processes and chemical products
Some VOCs can present health risks at concentrations well below those required to create a combustible atmosphere.
That is where PID monitoring can provide an important additional layer of detection.
PID vs LEL: what’s the difference?
An LEL sensor and a PID sensor are not measuring the same thing.
An LEL sensor is designed to determine the concentration of combustible gas relative to its Lower Explosive Limit. It is primarily concerned with whether the atmosphere is approaching a flammable or explosive concentration.
A PID is designed to detect many VOCs at much lower concentrations, generally reported in ppm.
For example, a VOC could potentially be present at a concentration relevant to worker exposure while remaining far below the concentration required to produce a significant LEL reading.
For applications where both toxic VOC exposure and combustible atmospheres are possible, monitoring PID + LEL provides much greater information than relying on an LEL sensor alone.
What does a multi-gas monitor with PID detect?
Control Hire’s PID gas monitoring configuration combines Photoionisation Detection with conventional multi-gas monitoring, allowing one portable instrument to monitor:
PID + LEL + Oâ‚‚ + Hâ‚‚S + CO
This provides monitoring for several different atmospheric hazards from a single unit.
PID
Detects a broad range of VOCs and other ionisable compounds.
LEL
Monitors combustible gases as a percentage of their Lower Explosive Limit.
Oxygen (Oâ‚‚)
Identifies oxygen-deficient or oxygen-enriched atmospheres.
Hydrogen Sulphide (Hâ‚‚S)
Detects toxic hydrogen sulphide gas, which can occur in sewers, wastewater infrastructure and other confined environments.
Carbon Monoxide (CO)
Detects carbon monoxide generated by combustion sources including engines, generators and other equipment.
Where are PID gas detectors used?
PID monitoring can be useful anywhere VOCs or unknown airborne contaminants may be present, including:
- Confined spaces
- Tunnels and underground works
- Stormwater and sewer infrastructure
- Contaminated land remediation
- Fuel and chemical storage areas
- Industrial maintenance
- Painting and coating works
- Solvent and adhesive use
- Tank entry and cleaning
- Spill response
- Wastewater facilities
- Construction and demolition
The correct sensor configuration should always be selected for the specific gases and substances that could reasonably be present.
Why use a PID instead of relying on smell?
Smell is not a reliable method of determining whether an atmosphere is safe.
Some hazardous substances may be detectable by smell before they become dangerous, while others may reach harmful concentrations without providing a reliable warning. Odour sensitivity also varies considerably between people.
Gas monitoring provides an objective measurement instead of relying on someone’s senses.
Hire PID Gas Detectors from Control Hire
Control Hire provides gas detection equipment for construction, infrastructure, confined-space and industrial applications across Australia.
Our multi-gas monitoring solutions can combine Photoionisation Detection (PID) with monitoring for LEL, oxygen, hydrogen sulphide and carbon monoxide, providing broader visibility of atmospheric hazards from a single portable instrument.
If you’re unsure whether a standard 4-gas monitor or a gas monitor with PID is appropriate for your application, speak with Control Hire about the gases, VOCs and site conditions you’re dealing with.
VOC around? Find out.