How do you calibrate a portable gas detector correctly?

To calibrate a portable gas detector correctly, you expose the device to a known concentration of calibration gas, allow the sensors to stabilize, and adjust the readings to match the reference values. Most modern detectors walk you through this process step by step. Calibration should be done at regular intervals and always after sensor replacement, exposure to high gas concentrations, or any period of storage. The sections below cover everything from bump tests to calibration gas selection and the most common mistakes to avoid.

What happens if a portable gas detector is not calibrated?

An uncalibrated portable gas detector can give inaccurate readings, either missing dangerous gas concentrations entirely or triggering false alarms. Both outcomes are hazardous. A detector that under-reads may give crew members false confidence when entering an enclosed space. A detector that over-reads can cause unnecessary evacuations and erode trust in the equipment over time.

In a maritime context, the stakes are particularly high. Enclosed space entry is one of the most dangerous activities on board a ship, and atmospheric testing is the primary safety barrier before anyone goes in. If the gas detector is not functioning accurately, that barrier fails silently. Under IMO Resolution MSC.581(110), which entered into force on 3 December 2025, pre-entry atmospheric testing is a hard requirement, and the results must be recorded. An unrecorded or inaccurate test is treated by Port State Control as a test that did not take place.

Beyond regulatory risk, there is a straightforward human safety argument: sensors drift over time due to exposure to contaminants, humidity, temperature fluctuations, and simple aging. A detector that was accurate six months ago may no longer be reliable today without proper calibration.

What is the difference between a bump test and a full calibration?

A bump test is a quick functional check that confirms a detector’s sensors respond to gas. A full calibration is a precise adjustment that corrects sensor readings to match a known reference concentration. Both are important, but they serve different purposes and should not be used interchangeably.

What a bump test does

During a bump test, you briefly expose the detector to a gas mixture and confirm that the alarm activates. It tells you the sensor is working and the alarm is functioning. It does not tell you whether the reading is accurate. A bump test takes only a few seconds and is typically performed before each use or at the start of each shift.

What a full calibration does

A full calibration exposes the detector to a precise concentration of calibration gas, measures the sensor’s response, and adjusts the internal settings so the displayed reading matches the actual concentration. This process corrects for sensor drift and confirms measurement accuracy. Full calibrations take longer and require the right calibration gas at the right concentration for each sensor type.

A common misconception is that a passed bump test means calibration is not needed. In practice, a bump test only confirms the sensor reacts, not that it reacts correctly. Both checks are part of a complete maintenance routine.

How often should a portable gas detector be calibrated?

Most manufacturers recommend a full calibration every three to six months, but the actual interval depends on how frequently the detector is used, the conditions it is exposed to, and the requirements of your Safety Management System. In high-use maritime environments, more frequent calibration is often appropriate.

Beyond scheduled intervals, a full calibration is always required after the following events:

Sensor replacement or battery replacement that affects sensor function
Exposure to gas concentrations significantly above the measurement range
Physical impact or dropping the device
Extended storage, particularly in conditions of high humidity or temperature
Any reading that appears inconsistent or suspect during a bump test

For vessels subject to Port State Control inspections, calibration records must be available and up to date. Classification societies and flag state administrations may have specific requirements, so always check the applicable standards for your fleet. Our service and repair team can advise on calibration schedules that align with your vessel’s inspection cycle.

What calibration gas do you need for a portable gas detector?

The calibration gas you need depends on the sensors fitted in your detector. Each sensor type requires a specific gas or gas mixture at a certified concentration, typically expressed in parts per million (ppm) or as a percentage of the Lower Explosive Limit (LEL). Using the wrong gas or the wrong concentration will produce an inaccurate calibration.

For a five-gas detector compliant with IMO Resolution MSC.581(110), you typically need a calibration gas mixture covering:

Oxygen (O₂): usually supplied as a reduced-oxygen mixture, for example 18% O₂ in nitrogen
Flammable gas (LEL): commonly methane or pentane at a certified LEL percentage
Carbon monoxide (CO): typically 50 to 100 ppm in air or nitrogen
Carbon dioxide (CO₂): a ppm-range mixture, since the regulatory limit is 5,000 ppm (0.5% by volume), requiring high-resolution NDIR sensor calibration
Hydrogen sulphide (H₂S): typically 10 to 25 ppm in air

Calibration gas cylinders have an expiry date and must be stored and handled correctly. Expired or contaminated calibration gas will produce unreliable results. Always use certified calibration gas from a reputable supplier and verify the certificate of analysis before use.

How do you perform a full calibration on a portable gas detector?

A full calibration follows a structured sequence: you prepare the equipment, expose the sensors to calibration gas, allow readings to stabilize, confirm or adjust the values, and record the result. The exact steps vary by manufacturer and model, but the general process is consistent across most portable detectors used in maritime applications.

Check the detector before starting. Confirm the battery is sufficiently charged, the sensors are within their service life, and the device is clean and undamaged.
Allow the detector to warm up. Power on the device and let it reach a stable baseline reading in fresh air before beginning. This typically takes one to two minutes.
Enter calibration mode. Follow the manufacturer’s procedure to access the calibration menu. Some detectors require a dedicated calibration kit or docking station.
Apply the calibration gas. Connect the calibration gas cylinder using the appropriate regulator and tubing. Apply the gas at the flow rate specified by the manufacturer, usually between 0.5 and 1 litre per minute.
Wait for the reading to stabilize. Allow the sensor to respond fully before confirming the value. Rushing this step is one of the most common calibration errors.
Confirm or adjust the reading. If the detector’s displayed value matches the calibration gas concentration within the acceptable tolerance, confirm. If not, adjust according to the manufacturer’s instructions.
Repeat for each sensor. Multi-gas detectors require each sensor to be calibrated individually or as part of a certified gas mixture.
Record the calibration result. Log the date, calibration gas used, results, and the name of the person performing the calibration. This record is required for Port State Control and classification society inspections.

If the detector fails calibration, do not return it to service. Tag it as out of service and arrange for inspection or sensor replacement before the next use. Our fire and gas detection specialists can support you with both the equipment and the technical guidance to keep your fleet compliant.

What are the most common calibration mistakes with portable gas detectors?

The most common calibration mistakes include using expired calibration gas, skipping the warm-up period, calibrating in a contaminated environment, and failing to record the results. Each of these errors can produce a detector that appears calibrated but does not measure accurately in the field.

Here is a practical overview of the mistakes to watch out for:

Using expired calibration gas. Calibration gas cylinders have a shelf life. After expiry, the concentration may have drifted, making your calibration inaccurate from the start.
Calibrating in a contaminated atmosphere. If background gases are present in the calibration environment, the sensor baseline will be wrong. Always calibrate in a clean, fresh-air environment.
Not allowing the sensor to stabilize. Reading the value too quickly, before the sensor has fully responded to the calibration gas, produces an incorrect adjustment.
Using the wrong gas concentration. Each sensor has a target calibration concentration. Using a cylinder with a different concentration without adjusting the procedure leads to an offset reading.
Skipping the CO₂ sensor. With the introduction of MSC.581(110), CO₂ is now a mandatory measurement parameter. Many older calibration routines were built around four-gas detectors and do not include CO₂ calibration. This gap must be closed.
Not recording the result. Calibration without documentation does not exist from a compliance perspective. Port State Control and classification society inspectors will ask for records.
Treating a bump test as a calibration. As covered earlier, these are two separate procedures. A bump test confirms function, not accuracy.

How Lavastica helps with gas detector calibration

Lavastica supports maritime teams with the full range of what calibration requires: the right equipment, the right parts, and the right expertise to keep detectors accurate and compliant. Whether you need a replacement sensor, a certified calibration kit, or a complete five-gas detector that meets the current IMO requirements, we can supply it quickly from our warehouse in Rotterdam.

Supply of portable gas detectors from more than 100 brands, including five-gas configurations compliant with MSC.581(110)
Calibration gas cylinders with valid certificates of analysis
Sensor replacements compatible with your existing detector models
In-house calibration, repair, and overhaul in our Rotterdam workshop
Technical advice on which equipment fits your current onboard installations
Fast worldwide delivery to minimize downtime when vessels are in port

If your fleet is due for a calibration check or you need to upgrade to a five-gas detector, get in touch with us. Learn more about our team or contact us directly for fast, practical advice.

Phone: +31 (0) 10 265 5070
Email: info@lavastica.com