A gas detection system at the blow-off point is strongly recommended, but not always legally required. In geothermal installations and nitrogen systems, gas detection can be life-saving, as certain gases are colourless and odourless. The necessity of an installation depends on the type of gas, the location and the applicable ATEX guidelines. This article answers the key questions about when you must install gas detection and how to make the right choice.
What is a gas detection system and why is it important at blow-off points?
A gas detection system detects dangerous gas concentrations in the air and automatically warns when safety limits are exceeded. At blow-off points of nitrogen systems and geothermal installations, this is crucial, as these gases are often invisible and odourless, meaning leaks can go unnoticed.
Blow-off points form potential risk areas, as gas is regularly released here during maintenance, malfunctions or the normal operation of blow-off valves. Nitrogen can, for example, cause oxygen displacement in enclosed spaces, which can lead to suffocation. In geothermal systems, toxic gases such as hydrogen sulphide are sometimes released.
The gas detection system works by continuously monitoring the air composition around the blow-off point. Modern systems can detect various gases simultaneously and provide both local and central alarms. They can also automatically activate ventilation systems or shut off the gas supply in case of danger.
Gas monitoring at blow-off points prevents accidents through early warning. This gives personnel time to safely leave the area and take measures before concentrations become dangerous.
When are you legally required to install gas detection?
Gas detection is legally required in ATEX zones, in enclosed spaces where toxic gases may be released and at installations above certain capacities according to the Major Accident Risks Decree. For geothermal projects, specific requirements apply, depending on the depth and gas composition of the thermal water.
The Dutch Working Conditions Act requires gas detection when employees are exposed to hazardous substances. This applies, for example, to:
- Enclosed spaces with nitrogen systems
- Geothermal installations with hydrogen sulphide
- Data centres with large quantities of nitrogen for fire suppression systems
- Laboratories with various gas lines
The ATEX directive 2014/34/EU stipulates that gas detection is mandatory in explosive atmospheres. This applies to zones where flammable gases may escape. Even if the gas itself is not flammable, by-products or other substances present may pose an explosion hazard.
Municipal permits for industrial safety may impose additional requirements. Always check local regulations and have a risk analysis carried out to determine whether gas detection is mandatory for your specific situation.
What types of gas detection systems are there for blow-off points?
There are three main types of gas detection systems: fixed detectors for permanent monitoring, portable detectors for mobile checks and combined systems. Fixed systems offer continuous monitoring and automatic alarming, whilst portable detectors provide flexibility for periodic measurements and different locations.
Fixed gas detection systems are ideal for blow-off points, as they offer 24/7 monitoring. They consist of sensors, control panels and alarm systems. These systems can be directly linked to ventilation systems and emergency stop switches.
Sensor technologies differ per gas type:
- Electrochemical sensors: suitable for toxic gases such as hydrogen sulphide
- Infrared sensors: detect carbon dioxide and hydrocarbons
- Oxygen measurement: essential in nitrogen systems due to oxygen displacement
- Catalytic sensors: for flammable gases and vapours
Portable detectors are useful for maintenance work and checks at various points. They are less suitable as the sole safety measure at permanent blow-off points, but form a good supplement to fixed systems.
Modern systems often offer multi-gas detection, allowing one device to monitor various hazards simultaneously. This is cost-effective and reduces maintenance complexity.
How do you choose the right location for gas detectors at blow-off points?
Place gas detectors within 1–3 metres of the blow-off point, taking into account gas density, prevailing wind direction and possible gas dispersion. Lighter gases require higher-placed detectors, heavier gases require detectors closer to the ground. Avoid locations with strong air currents that may disturb measurements.
Gas density determines the ideal height for placement. Nitrogen has approximately the same density as air and disperses evenly. Hydrogen sulphide is heavier and sinks downwards. Place detectors accordingly.
Important placement factors:
- Distance from blow-off point: 1–3 metres for optimal detection
- Height: adapted to gas density and expected dispersion
- Wind direction: take into account prevailing wind patterns
- Obstacles: avoid placement behind walls or equipment
- Accessibility: for maintenance and calibration
The ambient temperature affects sensor sensitivity. Extreme temperatures can cause false alarms or delay detection. Choose detectors suitable for the expected temperature range and protect them from direct sunlight or heat sources.
Install multiple detectors at large blow-off points or complex air flows. This prevents blind spots and increases detection reliability. Test the placement with smoke patterns or tracer gases to visualise gas dispersion.
What are the costs and maintenance requirements of gas detection systems?
Fixed gas detection systems cost between €1,500 and €5,000 per detection point, including installation. Portable detectors vary from €500 to €2,000 per device. The annual maintenance costs amount to approximately 10–15% of the purchase price, including calibration, sensor replacement and service visits.
The purchase costs depend on:
- The type of sensors and the number of gases to be detected
- Certification (ATEX, SIL rating)
- Communication capabilities (wired, wireless)
- Integration costs with existing systems
Calibration intervals vary per sensor type. Electrochemical sensors require calibration every 3–6 months, infrared sensors annually. Oxygen measurement must be checked monthly in critical applications.
Sensor replacement is a significant cost item. Electrochemical sensors last 2–3 years, infrared sensors 5–7 years. Reserve €200–€500 annually per detection point for sensor replacement and calibration.
The total cost of ownership over 10 years amounts to approximately double the purchase price. Quality systems have lower maintenance costs and a longer lifespan, which justifies the additional investment. Preventive maintenance prevents failure and significantly extends sensor life.
How Presscon helps with gas detection systems for blow-off points
We offer complete gas detection solutions, specially designed for blow-off points in nitrogen systems and geothermal installations. Our expertise in industrial safety and years of experience with complex projects ensure reliable, customised systems that perfectly match your specific situation and safety requirements.
Our gas detection services include:
- Risk analysis and advice: determination of detection requirements and optimal system configuration
- Custom systems: design and realisation of detection systems, adapted to your installation
- Integration: connection with existing nitrogen systems, ventilation systems and emergency stops
- Maintenance and calibration: preventive maintenance and legally required calibrations
- 24/7 service: rapid response to malfunctions and emergency situations
Through our experience in geothermal, data centres and laboratories, we understand the specific challenges of gas detection at various blow-off points. We provide ATEX-certified systems that comply with all Dutch and European safety standards, including ATEX vacuum pressure relief for complex installations.
Contact us for a non-binding risk analysis and a customised quotation. Our specialists will be happy to advise you on the best gas detection solution for your blow-off points and ensure a safe, compliant installation.
Frequently Asked Questions
How often must I have my gas detection system calibrated and what happens if I skip this?
The calibration interval depends on the sensor type: electrochemical sensors every 3-6 months, infrared sensors annually. Skipping calibration can lead to false alarms or missed gas leaks, resulting in legal fines and safety risks. Document all calibration sessions for compliance audits.
Can I install a gas detection system myself or do I always need a certified installer?
For ATEX zones and legally required installations, a certified installer is required. You can place simple portable detectors yourself, but fixed systems with alarm and ventilation connections require professional installation. Incorrect installation can lead to rejection during safety inspections.
What should I do if my gas detector regularly gives false alarms?
False alarms often indicate contaminated sensors, incorrect calibration or unsuitable placement. First check whether the detector is not exposed to dust, moisture or extreme temperatures. Have the system professionally cleaned and calibrated. Consider relocation if environmental factors are the cause.
How do I know if my existing gas detection system still complies with current safety standards?
Have a compliance audit carried out every 3-5 years by a certified safety specialist. Check whether your system complies with the latest ATEX guidelines and Dutch Working Conditions Act. Outdated systems may miss new gas types or have insufficient integration capabilities.
What backup measures should I have if my gas detection system fails?
Implement redundant detectors at critical locations and ensure portable backup detectors. Establish procedures for manual checks during system failure and train personnel in the use of portable equipment. Consider a maintenance contract with 24/7 breakdown service for critical installations.
Is gas detection also needed at temporary blow-off points during maintenance work?
Yes, temporary blow-off points can be even riskier due to unpredictable gas flows and limited ventilation. Use portable multi-gas detectors and ensure continuous monitoring during work. Establish a safety protocol with evacuation procedures and ensure all personnel present are trained in gas detection alarms.