Generator Safety Gear: CO Alarms, Cords and Transfer Switches

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Running a generator through an outage brings three avoidable hazards: carbon monoxide from a generator too close to the house, cords that can't carry the load, and generators plugged into a wall outlet to backfeed the house wiring. Each has a specific fix, and this page is those fixes — nothing else.

CPSC's guidance is short: run a portable generator outside only, at least 20 feet from the house with the exhaust pointed away; put battery-operated or battery-backup CO alarms on every level and outside sleeping areas, and test them monthly; use heavy-duty, outdoor-rated cords rated for more watts than everything plugged into them; and never plug a generator into a wall outlet. The products below are the hardware for those four rules.

An alarm is a backstop, not permission to place a generator badly, and a transfer switch is an electrician's install. Size the generator first with the generator sizing calculator, then decide whether cords are enough or you need circuits.

How we picked

Keeps working with the power out (sealed or backup battery)
Listed to the relevant safety standard — UL 2034 for CO, UL 217 for smoke, UL 1008 for transfer switches
Rated for the actual load and distance, with the limits stated plainly
Prevents the failure outright rather than warning about it where possible

We do not accept payment for placement and we do not publish star ratings we did not measure. Specifications come from each manufacturer's published spec sheet.

Side by side

Product	Type	Best for	Warranty	Power	Rating	Listing
Kidde COBD10 Carbon Monoxide Alarm	Battery CO alarm	Every level of the home and outside sleeping areas, before generator season	10-year limited	Sealed 10-year lithium battery (not replaceable)	—	—
Kidde 30CUD10-V Smoke + CO Alarm	Combination smoke + CO alarm	Hallways outside bedrooms, where a smoke alarm and a CO alarm are both needed	10-year limited	Sealed 10-year battery (not replaceable)	—	—
Southwire 12/3 SJTW 50 ft Outdoor Extension Cord (2588SW0002)	Outdoor extension cord	Running a fridge, freezer or space heater from a portable generator at a safe distance	—	—	15 A, 125 V, 1,875 W	UL certified (Southwire)
Reliance Controls Pro/Tran 10-Circuit Transfer Switch Kit (31410CRK / 310CRK)	Manual transfer switch kit	Portable generators up to 7,500 running watts with an L14-30 outlet	5 years	—	30 A, 125/250 V; generators up to 7,500 running watts	cULus listed to UL 1008

The picks

#1 · Battery CO alarm

Kidde COBD10 Carbon Monoxide Alarm

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A CO alarm on a sealed 10-year battery with a digital ppm display — it keeps working through an outage, which is exactly when a generator puts carbon monoxide near the house.

Best for: Every level of the home and outside sleeping areas, before generator season

Power: Sealed 10-year lithium battery (not replaceable)
Sensor: Electrochemical CO
Display: Backlit CO ppm readout with peak-level memory
Alarm: 85 dB at 10 ft
Standard: Meets UL 2034
Mounting: Wall or tabletop
Warranty: 10-year limited

Needs nothing from the grid — an outage can't silence it
Shows CO in ppm and remembers the peak, so an exposure while you slept is visible in the morning
The battery lasts the alarm's whole life — nothing to forget to replace

CO only — it does not detect smoke
The whole unit is replaced when it signals end of life at 10 years

Read the full write-up →

#2 · Combination smoke + CO alarm

Kidde 30CUD10-V Smoke + CO Alarm

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One sealed-battery unit that detects smoke and carbon monoxide and says which one it found — for the spots where one device has to do both jobs.

Best for: Hallways outside bedrooms, where a smoke alarm and a CO alarm are both needed

Sensors: Photoelectric smoke + electrochemical CO
Power: Sealed 10-year battery (not replaceable)
Alerts: 85 dB horn with voice alerts that name the hazard
Standards: Certified to UL 217 (10th ed.) and UL 2034 (5th ed.) — Intertek/ETL
Warranty: 10-year limited

Works through an outage — no mains power needed
Voice alerts tell smoke from CO, which changes what you do next
One device where two would otherwise be needed

Photoelectric smoke sensing only — Kidde itself recommends having both sensor types in the home
No CO ppm display, unlike the COBD10
Kidde recommends testing it weekly

Read the full write-up →

#3 · Outdoor extension cord

Southwire 12/3 SJTW 50 ft Outdoor Extension Cord (2588SW0002)

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A 50-foot, 12-gauge outdoor cord with a lighted end — the reach a portable generator needs to sit 20 feet from the house and still get power to what you're running.

Best for: Running a fridge, freezer or space heater from a portable generator at a safe distance

Conductors: 12/3 — 12 AWG copper, 3 conductors
Jacket: SJTW — vinyl, weather-rated
Length: 50 ft
Rating: 15 A, 125 V, 1,875 W
Plug: NEMA 5-15P, lighted end
Listing: UL certified (Southwire)

12 AWG holds voltage drop to about 2% at a full 15 A over 50 ft
The 20-foot CO distance plus the run to the appliance is exactly a 50-foot problem
Lighted end shows at a glance that the cord is live

Vinyl (PVC) jacket stiffens below freezing — for a cord that lives on the generator all winter, a rubber SOOW cord is tougher
15 A limit: keep the total of everything plugged into it under 1,875 W

Read the full write-up →

#4 · Manual transfer switch kit

Reliance Controls Pro/Tran 10-Circuit Transfer Switch Kit (31410CRK / 310CRK)

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A 30 A, 10-circuit manual transfer switch that mounts beside the panel, with the outdoor inlet box and generator cord in the box — the legal, no-backfeed way to run chosen circuits from a portable generator.

Best for: Portable generators up to 7,500 running watts with an L14-30 outlet

Rating: 30 A, 125/250 V; generators up to 7,500 running watts
Circuits: 10 — up to 10 single-pole or 5 double-pole
Factory breakers: (1) 2-pole 20 A, (2) 1-pole 20 A, (6) 1-pole 15 A
In the kit: Switch with 18 in pre-wired conduit, outdoor inlet box (PB30), 10 ft 30 A generator cord
Generator outlet: NEMA L14-30 (4-prong 120/240 V twist-lock)
Metering: Two wattmeters for balancing the load
Listing: cULus listed to UL 1008
Warranty: 5 years

Double-throw switches can't connect the generator and the utility at the same time — backfeeding is impossible in any position
Mounts beside the existing panel of any common brand; no panel replacement
Inlet box and cord included, so the generator stays outside at a distance

Electrician install, and usually a permit — check with your local inspector
Circuits lose AFCI/GFCI protection on generator power unless matching breakers are fitted in the switch
Not for electric water heaters, dryers, ranges or central A/C
Reliance renumbered the kit 310CRK; Amazon lists the older 31410CRK part number with the same core contents and ratings

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Working out what you need before you buy? Read the generators & backup power guides.