The Fireboy-Xintex CMD6 series is the marine-grade carbon monoxide detector required by ABYC A-24 on any gasoline-powered vessel with enclosed accommodation spaces. Replace every 5 years from the date of manufacture stamped on the back (not the install date), test monthly with the onboard self-test button and annually with a calibrated CO source, and install one detector per sleeping cabin plus one in the main saloon. USCG does not mandate CO detectors on uninspected recreational vessels, but ABYC compliance is the de-facto insurance standard and Florida marine surveyors will fail a pre-purchase survey without current detectors.
What is the CMD6 series and what does it replace?
The CMD6 is Fireboy-Xintex's sixth-generation marine carbon monoxide detector, replacing the long-running CMD5 line. It uses an electrochemical sensor calibrated for the higher humidity, salt-laden environment of a marine cabin, draws 12V or 24V DC, and incorporates a 95 dB alarm, a green/red status LED, and a self-test button. The CMD6 introduced a 5-year sensor life (up from 4 years on the CMD5), a tamper-resistant mounting bracket, and a serial interface that lets the unit network with Maretron N2K monitoring and Garmin OneHelm gateways.
Why are marine CO detectors required?
Carbon monoxide kills more boaters in Florida every year than fire and flooding combined. Generator exhaust, neighboring vessel exhaust at the slip, and 'station wagon effect' from outboard exhaust at low speeds can flood a cabin with CO in minutes. ABYC A-24 requires a CO detector in every enclosed accommodation space on any vessel with a fossil-fuel-powered engine, generator, heater, or stove. The USCG endorses A-24 in its Recreational Boating Safety guidance and Florida FWC officers cite detector absence on commercial passenger vessels under §327.
When do you replace a CMD6 detector?
| Trigger | Action | Reference |
|---|---|---|
| 5 years from manufacture date | Replace unit entirely — sensor cannot be re-celled | ABYC A-24.6.4 |
| End-of-life chirp | Replace immediately, even if under 5 years | Manufacturer guidance |
| After exposure to bilge water or fuel vapor | Replace — sensor is contaminated | Manufacturer guidance |
| Failed self-test | Replace within 7 days | ABYC A-24.6.5 |
| Annual test fails | Replace within 7 days | USCG / ABYC A-24 |
The manufacture date is stamped on the back of the unit as a 4-digit YYWW code. A unit stamped 2148 was built in week 48 of 2021 and must be replaced no later than week 48 of 2026 — even if it was installed brand-new in 2024. Always check the YYWW before installing a new-in-box unit; resellers occasionally have old stock.
How do you test a CMD6 monthly?
- Press and hold the self-test button on the face of the detector for 5 seconds.
- The red LED should flash and the alarm should sound at full 95 dB for 3 seconds.
- The unit returns to green LED steady within 10 seconds.
- Log the test in the vessel's fire-and-safety binder.
- If the alarm fails to sound, the LED stays red, or no response is observed, replace the unit within 7 days.
How is the annual calibrated test different?
Self-test verifies the alarm circuit and microprocessor but does NOT verify the electrochemical sensor is still detecting CO. Annual calibrated testing uses a measured 50 ppm CO source delivered through a hood over the sensor. A passing CMD6 alarms within 60 seconds. Greenfire performs this test dockside as part of annual certification and updates the detector log; vessels heading offshore or operating commercially should not skip it.
How many detectors do you need and where?
- One in each enclosed sleeping cabin, mounted on the overhead or upper bulkhead within 6 in of the ceiling
- One in the main saloon or galley if separately enclosed
- One in the pilothouse if it has a closing door and the helm is run from inside
- Not required in open cockpits, engine rooms (CO is overwhelmed there — fire detection is the right tool), or unventilated lazarettes
- Never mount within 12 in of an AC vent, hatch, or porthole — airflow delays detection
Wiring a CMD6 correctly
The CMD6 is hard-wired to a 12V or 24V always-hot circuit on a dedicated 1 A breaker. Do not put it on the cabin lighting circuit — when the master switch is off at the slip, the detector goes silent and a generator running at the next slip can fill an unattended cabin with CO. Use 16 AWG marine-tinned with crimp ring terminals at the detector and heat-shrink butt connectors at the trunk. Label the breaker 'CO DETECTORS — DO NOT SWITCH OFF'.
USCG and Florida compliance
| Vessel type | Requirement | Enforcement |
|---|---|---|
| Recreational < 65 ft, gasoline | ABYC A-24 (industry standard, not federal law) | Insurance and survey |
| Recreational, diesel only | Not required by ABYC, recommended | Insurance |
| Six-pack charter (OUPV) | ABYC A-24 + functional log | USCG annual inspection |
| Inspected passenger (Sub T/K) | 46 CFR 181 — fixed CO detection in accommodation | USCG |
| Florida bareboat charter | FWC §327 — operational CO detectors | FWC |
Cost to replace and install in 2026
Hardware: $135–$165 per CMD6 unit. Dockside swap-out (remove old unit, install new, test, log): $85 first unit + $35 per additional unit on the same visit. A typical 50 ft motoryacht with three sleeping cabins and a saloon = 4 detectors, replaced in a single 90-minute visit, totals $625–$770 turnkey. Bundled with annual fire-system certification, the per-unit install drops to $25.
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常见问题
Are CO detectors required on a diesel-only yacht?+
Not by ABYC, but recommended on any vessel with a diesel generator, diesel heater (Webasto, Eberspächer), or that rafts up next to gasoline boats. Insurance underwriters increasingly require them regardless of fuel type on vessels over 35 ft.
Can I replace the sensor instead of the whole unit?+
No. The CMD6 is a sealed unit; the electrochemical cell is not field-serviceable. Replacement is the only path.
What's the difference between CMD6 and CMD6MBL?+
The CMD6MBL is the same detector with an integrated mounting bracket and a longer 6 ft pigtail for new installations. The CMD6 (no suffix) uses screw terminals for replacement of existing CMD5 wiring without recrimping.
Does a CO detector replace a smoke detector?+
No — different sensors, different fires. ABYC A-24 covers CO. NFPA 302 covers smoke and heat. A complete cabin needs both.
Why did my CMD6 alarm at the dock for no reason?+
Most often: a neighboring vessel's generator exhaust drifted into your cabin, or a shore-side truck idled near your slip. Ventilate, reset, and verify with a portable CO meter if available. Persistent false alarms after ventilation mean the unit is contaminated and needs replacement.