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From a fire safety perspective, the garage is one of the highest-risk areas in the entire house. It contains a car or motorbike with a full tank, a reserve fuel can in the corner, a lawnmower, brushcutter, thinners and aerosols. At the same time, this is exactly where welding, grinding and work with power tools most often take place – in other words, with sources of sparks. However, a conventional smoke alarm will not respond to a petrol vapour leak, because no smoke is produced. This article explains why petrol vapours are so insidious, why standard fire detectors are not enough, and how the risk is addressed by the Evikon E2630-VOC petrol vapour detector.
In a garage, vapour leaks have two main sources – and both need to be kept in mind, whether it is a domestic garage or a company workshop:
Evaporation from vehicle fuel systems. Petrol is a highly volatile liquid – it evaporates even at normal temperatures. Leaking fuel lines, ageing hoses, damaged fuel cap seals or a flooded carburettor on older equipment release vapours continuously for as long as the vehicle is standing in the garage. With classic cars and carburettor-powered garden machinery, evaporation is practically unavoidable.
Storage of fuel and chemicals. Petrol cans, lawnmower and chainsaw tanks, as well as thinners, cleaning petrol, acetone or brake cleaners – all of these are sources of volatile organic compounds (VOCs). All it takes is a poorly tightened cap, a cracked canister or spilled fuel during decanting, and the vapour concentration in an enclosed space starts to rise. In winter, when the garage is closed and not ventilated, the risk is highest.
They all have one thing in common: petrol vapours are invisible, heavier than air and extremely flammable. The lower explosive limit (LEL) of petrol vapours is around 1.4% by volume in air – so it takes very little for an explosive atmosphere to form near the garage floor, where it can be ignited by a single spark from a tool, electrical switch or static discharge.
A standard domestic fire alarm relies on a smoke detector or, in some cases, a heat detector. In the event of a vapour leak, both types have one fundamental timing problem:
There is no smoke during the evaporation phase. Petrol evaporates without burning – the vapour concentration in the garage may already be deep in the danger zone, yet the smoke detector remains silent. It will only respond once there is already a fire, and with petrol that is usually too late: vapour ignition is virtually instantaneous and often explosive in nature.
A heat alarm only responds once a fire has started. The temperature in the garage does not rise before ignition. So a heat detector has nothing to detect – until something is already burning.
Detectors are mounted on the ceiling, while vapours stay near the floor. Even if a smoke alarm could theoretically respond to vapours, it is installed in the wrong place. Petrol vapours are 3–4 times heavier than air, sink to floor level and accumulate in the lowest points – around inspection pits, channels and thresholds.
The only method that detects the danger before an open flame or explosion occurs is gas detection – specifically detection of petrol vapours and other VOCs. That is why, for garages, workshops and fuel stores, it is recommended to supplement protection (or base it entirely) on a gas detector that activates ventilation and an alarm at only a fraction of the explosive concentration.
If there were only a car in the garage, monitoring petrol vapours would be enough. In practice, however, the garage is also a workshop and a store. In addition to petrol, the semiconductor sensor in the E2630-VOC detector also responds to acetone, benzene, ethanol, ethyl acetate, toluene, xylenes and other organic substances – exactly the vapours from thinners, paints, cleaners and adhesives that are commonly stored in garages. A single detector therefore covers all typical sources of flammable vapours at once – regardless of how the concentration starts to rise.
The detector is factory-calibrated directly for petrol vapours (the reference substance is hexane C₆H₁₄, the main component of petrol vapours) and measures in the range 0–100% LEL. The alarms are set in two stages – the first stage at 10% LEL, the second at 20% LEL – so action can be taken long before the concentration even approaches the explosive limit.
The Estonian manufacturer Evikon MCI designed the E2630-VOC detector specifically for this type of application. In a single wall-mounted IP65 enclosure, it combines four functions:
This means you can solve detection, signalling and automatic garage ventilation with a single device – without needing to purchase a separate siren or fan switching module.
For petrol vapours, the detector uses a metal oxide semiconductor (MOS) sensor. The sensor measures changes in the conductivity of the sensitive layer when it comes into contact with flammable vapours – a method that is stable and reliable over the long term even in demanding garage conditions. The measuring range is 0–100% LEL with 0.1% LEL resolution, the signal is updated every second and the response time is up to 120 seconds. Sampling is by diffusion – vapours reach the sensor through natural air circulation, so no pump or sampling line is required.
The detector operates in a two-stage mode. When the first threshold is reached (factory setting 10% LEL), the first relay switches – typically to start the fan. At the second threshold (20% LEL), the second relay switches and the built-in 85 dB siren is activated together with a flashing LED. After the area has been ventilated, the alarm resets automatically; using a magnetic key, it can also be switched to manual mode, in which the alarm remains active until acknowledged by the operator.
The semiconductor sensor has an expected service life of more than 5 years, and the detector itself is designed for long-term unattended operation. To maintain measurement accuracy, the manufacturer recommends recalibration at intervals of 6–12 months – and for fixed flammable gas detectors this is also a legal requirement. Each package includes a factory calibration certificate, and recalibration can be conveniently arranged by post via the kalibrovat.cz service, including free email reminders of the due date.
The E2630-VOC offers two ways of connecting to surrounding equipment:
Two power supply versions are available: 230 VAC for direct connection to the garage electrical installation, and 24 V AC/DC for connection to a security or control system with backup power.
Technical specifications at a glance:
When installing a petrol vapour detector in a garage, it is worth following a few rules:
Mount the detector low above the floor. Petrol vapours are heavier than air and sink downwards – exactly the opposite of hydrogen or natural gas. The detector should therefore be installed approximately 30–60 cm above floor level, ideally near the lowest point in the space (inspection pit, floor slope) and close to the likely source of the leak, for example near the vehicle parking position or shelving with fuel cans.
Think about ventilation. Detection alone will not remove the vapours. The first alarm stage should be used to start the fan – ideally with extraction at floor level, where the vapours accumulate. The second stage should then be reserved for the main alarm: siren, beacon, or possibly sending a message via the security system.
Avoid interfering influences. Do not install the detector directly above a vehicle exhaust, near sources of strong vibration, or in places where silicone sprays are used – these damage the semiconductor sensor over time. Before painting or intensive work with thinners, bear in mind that the detector will respond – this is not a false alarm, but correct operation.
Do not forget recalibration. A fixed flammable gas detector is subject to mandatory annual calibration. By registering the detector at kalibrovat.cz, you will receive a free email reminder one month before the calibration certificate expires.
A petrol vapour detector is to a garage what a smoke detector is to a living room – the first line of defence. The difference is that with petrol it is often the only way to detect danger before ignition or explosion occurs, because the vapours are invisible, give no warning, and do not trigger a smoke alarm. The Evikon E2630-VOC detector combines everything a garage or workshop needs in one compact device – sensitive detection of petrol and other VOCs, a two-stage alarm, built-in siren and relays for automatic ventilation start-up – and thanks to its robust IP65 enclosure, it operates reliably all year round even in an unheated garage.
A smoke alarm only responds to combustion products – in other words, only once something is already burning. Petrol vapours, however, evaporate without smoke and without any rise in temperature, so neither a smoke detector nor a heat detector will detect them. In addition, vapour ignition is often explosive in nature, so there is no time left to react after ignition. A VOC detector detects a dangerous concentration already at 10% of the lower explosive limit – long before anything can happen.
Low above the floor, approximately 30–60 cm. Petrol vapours are 3–4 times heavier than air, sink to floor level and accumulate in the lowest parts of the garage – around inspection pits, thresholds and channels. Ceiling mounting, common for natural gas or hydrogen detectors, is a mistake with petrol: the detector would detect the leak with unnecessary delay, or not at all.
Yes. In addition to petrol vapours, the E2630-VOC semiconductor sensor also responds to acetone, benzene, ethanol, ethyl acetate, toluene, xylenes and other volatile organic compounds – in other words, vapours from thinners, cleaning petrol, paints, adhesives and cleaners. One device therefore covers all typical sources of flammable vapours in a garage or workshop.
Yes. The detector has two SPDT output relays with a maximum load of 250 VAC / 30 VDC, 5 A – so it can switch a standard garage fan directly, without an auxiliary contactor. The relay contact can also be wired in parallel with a manual switch, so you can start the fan yourself at any time and the detector will switch it on automatically in the event of an alarm.
Yes. The manufacturer recommends recalibration at intervals of 6–12 months, and for fixed flammable gas detectors annual calibration is also a legal requirement. A factory calibration certificate is included in the package. Recalibration can be arranged by post within 72 hours via kalibrovat.cz, and after free detector registration the service will automatically notify you by email when the due date is approaching.
Yes. The detector’s operating range is –40 to +70 °C at humidity up to 95% RH, and the enclosure is rated IP65, so dust and splashing water are not a problem. An unheated, damp or dusty garage is therefore no issue. The detector should simply not be installed in places with strong vibration, electromagnetic interference, or where silicone sprays are used – these damage the semiconductor sensor.
LEL (Lower Explosive Limit) is the lowest vapour concentration in air at which the mixture can explode. The detector signals the first alarm already at 10% of this limit (starting ventilation) and the second at 20% (main alarm with siren). Intervention therefore comes when the concentration is still 5–10 times lower than what is needed for ignition. After the area has been ventilated, the alarm resets automatically.
For a standard garage, the simplest option is 230 VAC – you connect the detector directly to the existing electrical installation, and power consumption is below 2 VA. The 24 V AC/DC version is suitable where you want to power the detector from a security or control system with a backup power supply, so detection continues to operate even during a power cut. Otherwise, both versions are functionally identical.
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