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FORENSICS DETECTORS FD · Volatile Organic Compounds VOC Detector by Forensics | Industrial Wall Mount | USA NIST Calibration | Explosion Proof | Adjustable Sound & Light Alarms | Relay Output | 0-100 ppm VOC |
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The Forensics Detectors VOC Detector is a fixed, mains powered gas detector intended to be mounted where solvent vapours accumulate and to switch ventilation or alarms through its two relay outputs. Its value is in the relays and the Exd IIC T6 Gb housing, not in a display reading. The listing publishes the range (0-100 ppm), the analogue output (4-20 mA), the remote control distance (up to 8 m) and the protection grade, but it does not publish the sensor technology, the alarm set points, the response time or the resolution. Buy it only if you have a defined trigger action and a fixed mounting position; for portable checks or general indoor air quality, a handheld or a multi-parameter monitor is the right tool.
What the sensor is doing, and what the listing will not tell you
A VOC detector of this class works by exposing a sensing element to air drawn or diffused into the housing. Volatile organic compounds reach the element and change an electrical property that the electronics convert into a concentration reading and a switching decision. The common sensing technologies for fixed industrial VOC detection are photoionisation (PID, using a UV lamp to ionise molecules), catalytic bead or metal oxide semiconductor elements, and electrochemical cells. Each has a different response to different compounds, a different cross-sensitivity profile and a different maintenance burden. The listing for this unit does not state which technology is inside. That is the single most important omission, because a PID responds broadly to many solvents, a metal oxide sensor responds to some compounds and is sensitive to humidity, and an electrochemical cell is usually tuned to one gas family.
What the listing does publish is the working range: 0-100 ppm. That figure defines the span over which the instrument is calibrated, not a safe level. A detector that reads to 100 ppm will still alarm at a set point you configure, and the listing does not publish the factory set points, the alarm delay, the resolution or the response time. Ask the supplier for those four figures before you mount the unit, because they determine whether the relay closes fast enough to protect the space.
The calibration claim is also narrower than it sounds. The listing states USA NIST calibration and that the unit arrives with a calibration and QA certificate. It does not state the calibration gas, the concentration used, the interval recommended, or whether the certificate is traceable to a specific standard. For a fixed detector, calibration is a recurring task, not a one-off event. Treat the supplied certificate as a starting point and plan a calibration schedule with the gas mix appropriate to the compounds you expect. The site’s guide to gas detector calibration kits explains what a kit needs to include.
The relay outputs are the reason to buy this instead of a monitor
A fixed detector earns its place when it does something. This unit has two relay alarm triggered switches rated 50 W, and the listing says they can control fans, pumps, electrical items, garage doors or additional alarms. That is the mechanism that turns a reading into an action: when concentration crosses the set point, the relay changes state and the ventilation starts. The 50 W rating is modest. It is enough to switch a contactor coil or a small fan, but not to drive a large motor directly. In practice you use the relay to energise a contactor or a relay board, and the contactor carries the load. The listing does not publish the relay contact type (normally open or normally closed), the contact rating in voltage and current, or whether the relay is latching. Those details matter for wiring a fail-safe circuit, so obtain them from the supplier.
The analogue 4-20 mA output is the other integration route. It lets the detector feed a building management system or a chart recorder, with 4 mA representing the bottom of the range and 20 mA the top. The listing does not state what the 4 mA and 20 mA values correspond to, so confirm whether 4 mA is zero ppm and 20 mA is 100 ppm, and whether the output is active or passive. The remote control is stated as up to 8 metres, which is useful for adjusting alarm settings from outside a contaminated area, but the listing does not describe the remote’s functions or whether it is supplied.
This is the point where the product differs from a wall mounted CO2 logger. A CO2 monitor records and displays; this detector switches. If your need is to understand a room’s air over time, the site’s comparison of CO2 and VOC monitoring is the better starting point.
Explosion proof, dust proof, water proof: what the grades actually cover
The listing states an explosion proof grade of Exd IIC T6 Gb and an IP65 housing rating. Those are separate claims. The Exd marking means the enclosure is flameproof: an internal ignition is contained and the hot gases are cooled as they escape, so the surrounding atmosphere is not ignited. The II C gas group covers the most easily ignited gases, and T6 is the temperature class with the lowest permitted surface temperature, 85 degrees Celsius. The Gb suffix indicates the equipment protection level for a zone where an explosive atmosphere is occasionally present. IP65 means dust tight and protected against water jets. Together these grades make the unit suitable for mounting in a plant room, a paint store or a solvent handling area where a spark from ordinary equipment would be a risk.
The grades do not make the detector intrinsically safe for portable use, and they do not remove the need for correct installation. Flameproof enclosures depend on the cable gland and the sealing being to the same standard. The listing does not publish the cable entry type, the gland size or the installation instructions, so the installer must confirm those. The listing also does not state the operating temperature range or the humidity range, both of which affect sensor behaviour and are usually printed on the certification label.
Do not read the explosion proof claim as coverage of every hazard. This is a VOC detector. It is not a combustible gas detector for methane or LPG unless the sensor is specified for those gases, and it is not a carbon monoxide detector. The listing makes no claim to detect CO, and a VOC sensor should not be relied on for it. If the space has fuel burning appliances, a separate CO alarm is required.
Where a fixed detector is the wrong instrument
The detector is designed to be mounted and left. It is not a survey tool. If you want to find where solvent vapour is coming from, or check a room after painting, a handheld instrument or a multi-parameter monitor is the correct purchase. The site’s guide to checking whether a monitor measures real VOCs sets out the questions to ask of any VOC reading, and the same questions apply here: which compounds, which sensor, which calibration gas.
It is also not a general indoor air quality monitor. It does not publish a CO2 measurement, a particulate measurement or a temperature and humidity reading, and the listing makes no claim to any of them. A household or office wanting to track ventilation should look at a multi-parameter unit instead. The site’s air quality monitor comparisons cover that category.
Finally, the unit needs mains power and a fixed wiring point. The listing does not state the supply voltage, the power consumption or whether a battery backup exists. Confirm the supply from the supplier before planning the installation, because a detector that loses power loses detection.
Installation and maintenance nobody mentions
The listing gives the range, the outputs and the housing grade, and it stops there. What it does not give is the mounting height, the sensor orientation, the warm-up time, the calibration interval or the expected sensor life. Those are not optional details. VOC vapours vary in density: a solvent such as toluene is heavier than air and accumulates low, while acetone is lighter and rises. The correct mounting height depends on the compound you are detecting, and the listing does not state a recommendation. Ask the supplier for the installation guide before you drill.
The maintenance burden is real. A fixed detector needs periodic calibration with a known gas, and a sensor replacement at the end of its life. The listing states a one year limited warranty and a calibration and QA certificate on arrival, but it does not state the recommended calibration interval or the sensor life. A common failure in fixed installations is a detector that is mounted, trusted and never checked. Build the calibration into the maintenance schedule from day one, and keep the certificate with the unit.
The alarm behaviour also needs a test. The listing states an adjustable audio and visual alarm and a large LED and buzzer, but it does not publish the sound pressure level in decibels or the flash rate. Test the buzzer and the relay with the remote or the set point adjustment after installation, and record the result. If the detector is in a noisy plant room, confirm the alarm is audible above background before relying on it.
The verdict on the Forensics Detectors fixed VOC detector
This is a specialist fixed detector for a defined job: mount it where solvent vapour can accumulate, wire the relay to a fan or an alarm, and maintain it on a calibration schedule. The explosion proof housing, the two relay outputs and the 4-20 mA output are the reasons to choose it, and the listing publishes those clearly. The gaps are equally clear: sensor technology, alarm set points, response time, resolution, supply voltage, relay contact details and calibration interval are all unpublished. A buyer who can obtain those figures from the supplier has a workable industrial detector. A buyer who wants a reading on a screen, a portable survey or a general indoor air quality picture should choose a different instrument.
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Frequently Asked Questions
Does this detector measure CO2 as well as VOCs?
No. The listing describes a volatile organic compounds detector with a 0-100 ppm range and makes no claim to CO2 measurement. CO2 and VOCs are different measurements with different sensors. If you need CO2, choose a CO2 monitor.
What sensor technology is inside?
The listing does not state it. Fixed VOC detectors commonly use photoionisation, metal oxide semiconductor or electrochemical sensors, and the choice affects which compounds are detected and how often the unit needs calibration. Ask the supplier before purchase.
Can I use it as a portable detector?
No. It is a wall mounted, fixed installation with a flameproof housing and wired outputs. It is not designed to be carried. For portable checks, use a handheld instrument.
What do the relay outputs switch?
The listing states two relay alarm triggered switches rated 50 W, intended to control fans, pumps, electrical items, garage doors or additional alarms. 50 W is a modest rating, so use the relay to energise a contactor rather than a large load directly.
How often does it need calibration?
The listing does not publish a calibration interval. It states that the unit arrives with a calibration and QA certificate and USA NIST calibration. A fixed detector needs periodic calibration with a known gas, so confirm the recommended interval with the supplier.
Is it suitable for a home garage?
It can be installed in a garage if the wiring and mounting are appropriate, but it is an industrial fixed detector with explosion proof housing and relay outputs. For a home workshop wanting a reading rather than a switching action, a portable or multi-parameter monitor is simpler and more informative.
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