Gas Detectors on Board

Admin
May 24
3 min read

Updated: May 25

🛑 Gas Detectors on Board – What Every Seafarer Must Know

On board any vessel, one of the most critical components of safety is early detection of hazardous gases. Whether in confined spaces, tanks, engine rooms, or cargo areas, gas detectors are essential for protecting crew and ensuring compliance with international regulations.

This post provides a practical guide to onboard gas detection — why it’s used, how it works, what gases to monitor, and how to properly use and test your device. We’ll also introduce three popular models used in the maritime industry: Dräger X-AM 2500, Dräger X-AM 5600, and MSA Altair 5X.

🚨 Why Gas Detection Is Critical

Gas detection systems serve to:

Alert crew to toxic gas levels (e.g. H₂S, CO, SO₂)
Detect flammable gases before reaching explosive limits
Monitor oxygen levels to avoid asphyxiation or fire risks
Ensure safety in confined space entries
Comply with SOLAS, MARPOL, and ISM Code requirements

🧪 Common Gases Detected Onboard

Gas	Purpose of Detection
O₂ (Oxygen)	Too low → asphyxiation risk, too high → fire hazard
CO (Carbon Monoxide)	Highly toxic; colorless, odorless, lethal in confined spaces
H₂S (Hydrogen Sulphide)	Extremely toxic; common in tanks, slops, sewage
CH₄ / LEL (Methane/flammable gases)	Explosion risk; detected via LEL (Lower Explosive Limit)
SO₂ / NO₂ / NH₃	Toxic byproducts; engine and cargo gases
CO₂ (Carbon Dioxide)	High concentrations reduce oxygen; dangerous in holds, scrubbers

🧰 How to Use a Gas Detector

Basic Operating Procedure:

Fresh Air Setup (Zero Calibration)
Calibrate the detector in clean air before entry.
Pre-entry Check
Insert the probe into the space from outside (e.g., via extension hose up to 45m).
Continuous Monitoring
Keep the device active and observe alarms during entry.
Regular Function Test (Bump Test)
Apply a certified gas to verify sensor response — usually monthly or before use.
Full Calibration
Every 6–12 months or after sensor warning/failure.