Marine safety service
Gas Detection Equipment
Supply, calibration, bump testing and repair of portable and fixed gas detectors for enclosed space entry, tanker cargo areas and gas-fuelled ships.
Overview
Marine gas detection equipment: calibration, servicing and supply
Marine gas detection equipment is the first line of defence against the atmospheres that kill seafarers in enclosed spaces: oxygen deficiency, flammable vapours, hydrogen sulphide and carbon monoxide. This service covers the portable multi-gas meters crew use before entering tanks, holds and void spaces, the single-gas personal monitors worn during entry, and fixed detection systems installed in tanker double-hull spaces, cargo pump rooms, gas carrier cargo areas and the fuel preparation spaces of gas-fuelled ships.
Sensors drift and filters block over time, so regular calibration with certified test gas and correct bump testing are essential. vslSafety coordinates calibration, repair, sensor replacement and supply of approved instruments through providers at the vessel’s port.
Regulatory requirements and standards
SOLAS regulation XI-1/7, introduced by resolution MSC.380(94) and in force since 1 July 2016, requires every ship to which SOLAS chapter I applies to carry an appropriate portable atmosphere testing instrument or instruments. As a minimum, they must measure oxygen, flammable gases or vapours, hydrogen sulphide and carbon monoxide before entry into enclosed spaces, and suitable means must be provided for the calibration of all such instruments. MSC.1/Circ.1477 gives guidelines to help select suitable portable instruments.
For tankers, SOLAS chapter II-2 regulation 4.5.7 requires portable instruments for measuring oxygen and flammable vapour concentrations, with means of calibration. Oil tankers of 20,000 tonnes deadweight and above constructed on or after 1 January 2012 must also have a fixed hydrocarbon gas detection system complying with chapter 16 of the FSS Code, covering ballast tanks and void spaces of the double-hull and double-bottom spaces adjacent to cargo tanks. MSC.1/Circ.1370 contains the guidelines for the design, construction and testing of these fixed systems. Gas carriers and gas-fuelled ships carry further fixed and portable detection requirements under the IGC Code and IGF Code.
Enclosed space entry itself is governed by the ship’s safety management system. In June 2025 the IMO adopted revised Recommendations for entering enclosed spaces aboard ships by resolution MSC.581(110), replacing resolution A.1050(27). The revised text places emphasis on an enclosed space register, risk assessment and training in the maintenance, calibration and use of atmosphere testing equipment. Servicing is normally done by a maker-authorised centre or competent laboratory using traceable test gas.
Inspection and calibration intervals
| Item | Requirement | Interval | Reference |
|---|---|---|---|
| Portable multi-gas meter | Bump test with known gas | Before each day’s use or as the maker specifies | Maker’s manual, SMS |
| Portable multi-gas meter | Full calibration with certified gas | Per maker, commonly every 6–12 months, and after any failed bump test | SOLAS XI-1/7, maker |
| Sensors (O2, LEL, H2S, CO) | Replacement | At end of rated life or when calibration fails | Maker |
| Fixed hydrocarbon gas detection (oil tankers) | Functional test and calibration | Per maker and the approved system manual | SOLAS II-2/4.5.7.3, FSS Code ch. 16, MSC.1/Circ.1370 |
| Calibration gas cylinders | Certificate validity | Replace before expiry date on the certificate | Supplier certificate |
| Enclosed space entry and rescue drill | Drill using the instruments | At least every two months | SOLAS III/19 |
What the service includes
- Inventory of all portable, personal and fixed detectors, with serial numbers and last calibration dates
- Visual inspection of housings, displays, filters, sample pumps, hoses and probes
- Full calibration against certified, traceable test gas and adjustment of zero and span
- Alarm set-point verification for oxygen, LEL, H2S and CO channels
- Sensor and battery replacement, with records of sensor installation dates
- Functional test of fixed detection systems, sampling lines, alarms and panel indications
- Supply of calibration gas, regulators and bump test stations
- Supply of replacement or additional approved instruments where units are beyond economic repair
- Issue of calibration certificates and a defect list for the vessel’s records
Equipment and system types covered
Providers commonly handle portable four-gas meters, single-gas personal monitors, combined oxygen and hydrocarbon meters for tanker use, infrared instruments for measuring hydrocarbon in inert atmospheres, toxic gas tube pumps, and fixed detection systems with sampling or point sensors. Makers frequently encountered on board include Dräger, MSA, Industrial Scientific, Honeywell BW, Riken Keiki and Crowcon, but the service applies to any make where test gas and parts are available.
Common defects and PSC deficiencies
- Calibration overdue or no calibration certificate on board
- No calibration gas on board, or the test gas is past its expiry date
- Instruments that do not measure all four required gases under SOLAS XI-1/7
- Crew unable to demonstrate bump testing or correct operation of the meter
- Blocked filters, failed pumps or sensors that will not reach span
- Fixed gas detection sampling points or alarms not working, or fault indications left unresolved
- Enclosed space entry drills not recorded at the required frequency
Certificates and documents you receive
- Calibration certificate for each instrument, showing test gas values, readings and next due date
- Test gas cylinder certificates with traceability and expiry dates
- Service report listing sensors, batteries and parts replaced
- Fixed system test report where the fixed installation was included
- Defect list and recommendations for any unit taken out of service
How to prepare the vessel
Collect all portable instruments, charged and with their hoses and probes, together with the instrument list and last certificates. If the fixed system is to be tested, arrange for an officer familiar with the panel and confirm that cargo operations permit access to sampling points. Where the service is done ashore, agree the collection and return times so the ship is never left without a working instrument for enclosed space entry; spare or loan units may be needed.
Pair this attendance with calibration services for other shipboard instruments, or with breathing apparatus servicing so enclosed space rescue equipment is checked at the same call.
Information needed for a quotation
- Vessel name, IMO number, flag, class and vessel type
- Port, berth or anchorage, ETA and ETD
- Maker, model and serial number of each instrument, and quantity
- Gases measured by each unit and last calibration date
- Fixed system maker, model and number of sampling points, if included
- Calibration gas, sensors or new instruments required
- Whether on-board attendance or shore workshop service is preferred
vslSafety then coordinates a suitable provider at the vessel’s port and confirms scope, timing and cost before attendance.
Frequently asked questions
How often should a portable gas detector be calibrated on a ship?
SOLAS XI-1/7 requires suitable means of calibration but does not fix a single interval. In practice the maker’s instructions govern, and most makers call for a full calibration with certified test gas at intervals of six to twelve months, plus a bump test before use. Any instrument that fails a bump test, has been dropped, or has had a sensor replaced should be fully calibrated before being used again for entry.
What gases must a shipboard atmosphere testing instrument measure?
As a minimum, SOLAS XI-1/7 requires instruments able to measure oxygen, flammable gases or vapours, hydrogen sulphide and carbon monoxide. Ships carrying particular cargoes may need additional capability, for example toxic vapours from chemical cargoes, or instruments able to measure hydrocarbon in inert gas atmospheres on tankers.
What is the difference between a bump test and calibration?
A bump test briefly exposes the sensors to a known gas to confirm that they respond and that alarms activate. It checks function but does not adjust the readings. Calibration compares the instrument against certified test gas of known concentration and adjusts zero and span so that readings are accurate. Bump testing is normally done by the crew before use; calibration is usually done by a competent service centre or by trained crew using the maker’s procedure and certified gas.
Which tankers need a fixed hydrocarbon gas detection system?
Oil tankers of 20,000 tonnes deadweight and above constructed on or after 1 January 2012 must be fitted with a fixed hydrocarbon gas detection system complying with chapter 16 of the FSS Code. It monitors ballast tanks and void spaces in the double-hull and double-bottom spaces adjacent to cargo tanks.
