First Alert SMCO600NV-AC SC5 Hardwired Smart Smoke and CO Alarm (Interconnectable)
$129.98
$129.99
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EDITORIAL REVIEW: 4.5/5 WC Safety Review — First Alert SMCO600NV-AC SC5 Hardwired Smart Smoke and CO Alarm Editorial assessment by the WC Safety Editorial Team, based on published First Alert specifications and ca...
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EDITORIAL REVIEW: 4.5/5 WC Safety Review — First Alert SMCO600NV-AC SC5 Hardwired Smart Smoke and CO Alarm
Editorial assessment by the WC Safety Editorial Team, based on published First Alert specifications and category fit. We did not laboratory-test this product.
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First Alert SMCO600NV-AC SC5 Hardwired Smart Smoke and CO Alarm (Interconnectable) Overview
The First Alert SMCO600NV-AC SC5 is a hardwired combination smoke and carbon monoxide alarm that puts two critical sensors in one ceiling unit. It detects both smoke from a developing fire and carbon monoxide (CO) gas, so you protect a room without mounting two separate devices. Because carbon monoxide is colorless and odorless, an alarm is the only reliable way to know it is present.
This unit wires into your home's 120V AC circuit and is interconnectable with compatible First Alert and BRK hardwired alarms. When connected in a series, a hazard detected by any one alarm triggers every alarm in the home at once, which buys precious seconds for occupants in distant bedrooms. A battery backup keeps the alarm working through a power outage.
Combination units like this belong on every level and outside each sleeping area. For whole-home coverage, pair it with standalone units from our combination smoke/CO alarms and dedicated CO detectors. New to layout planning? Start with our CO detector placement guide and the roundup of the best smoke detectors.
This alarm is a fixed combination unit; First Alert does not publish a user-selectable sensor mode, and we do not list a sensor technology, battery chemistry, or display specification that the manufacturer has not stated. Replace the entire unit at the end-of-life date marked on the housing.
What It Is Built For
| Use case | Fit | Buyer guidance |
|---|---|---|
| Whole-home hardwired protection | Ideal | Wires into 120V AC and interconnects with compatible First Alert/BRK alarms so every unit sounds together. Install on every level and near each bedroom. |
| Replacing an existing hardwired smoke + CO alarm | Ideal | Drop-in upgrade for homes already wired for combination alarms; uses standard interconnect wiring. Confirm your existing harness is compatible. |
| Bedroom and hallway coverage | Strong | Combination smoke + CO sensing covers two hazards outside sleeping areas in one ceiling unit. CO mixes evenly with air, so mounting height is flexible. |
| Power-outage resilience | Strong | Battery backup keeps the alarm active when AC power is lost. Keep the backup battery fresh per the manufacturer schedule. |
| Renters or homes without alarm wiring | Limited | This is a hardwired unit and needs 120V wiring. For non-wired spaces choose a battery or plug-in alarm instead, such as the Kidde KN-COPP-B-LPM. |
| Garage, RV, or fuel-appliance monitoring | Not suited | Smoke sensing is not rated for dusty/dirty garages. For a portable plug-in CO unit see the Kidde KN-COP-DP-10YL; for industrial gas exposure use a multi-gas meter. |
A smoke alarm and a carbon-monoxide alarm detect different hazards — install both (or a combination unit) on every level and near each sleeping area, and interconnect them where possible. Test monthly and replace at the unit's end-of-life date (CO sensors typically last 5–10 years; smoke alarms about 10). Carbon monoxide is colorless and odorless, so a working alarm is your only warning — look for UL 2034 (CO) / UL 217 (smoke) listing. See how to test a smoke & CO alarm and the CO detector placement guide.
Pros & Cons
Pros
- One unit senses both smoke and carbon monoxide, reducing the number of devices needed per room
- Hardwired to 120V AC for continuous power without routine battery swaps as the primary source
- Interconnectable so a hazard at any unit sounds every connected alarm in the home
- Battery backup maintains protection during a power outage
- Drop-in replacement for homes already wired for combination alarms
Cons
- Requires 120V household wiring; not an option for renters or rooms without an alarm circuit
- Manufacturer sensor technology (ionization vs photoelectric) is not published, so smoldering-vs-flaming bias is unspecified
- Combination units must be replaced as a whole at end of life rather than swapping a single sensor
- Smoke sensing is not suited to dusty garages or workshops
How It Compares
Within First Alert's combination lineup, the SMCO600NV-AC SC5 is the hardwired, interconnectable option for whole-home wiring. The SMCO100V-AC is a plug-in combination smoke + CO alarm for outlets, better suited to homes without an alarm circuit. For CO-only coverage with a digital readout, the battery First Alert CO250 or the wireless-interconnect First Alert CO511 are alternatives. Choose the SMCO600NV-AC when your home is already wired for hardwired alarms and you want every unit to sound together; choose a plug-in or battery model when wiring is not available. Compare full ranges in smoke detectors and carbon monoxide alarms.
Specifications
| Detects | Smoke and carbon monoxide (combination alarm) |
| Model | First Alert SMCO600NV-AC (SC5 series) |
| Power | Hardwired 120V AC with battery backup |
| Interconnect | Interconnectable with compatible First Alert / BRK hardwired alarms |
| Mounting | Ceiling / wall, hardwired junction box |
| Sensor type | Not specified by manufacturer |
| Standards | Smoke alarms certified to UL 217; CO alarms to UL 2034 (combination units meet both) |
| Placement | Every level and near each sleeping area; CO mixes with air so height is flexible |
| Replacement | Replace entire unit at end-of-life date on housing (CO sensors typically last ~5-10 years) |
Related Resources
CO detectors smoke detectors carbon monoxide alarms combination smoke/CO alarms gas detectors best CO detectors best smoke detectors CO detector placement guide how to test a smoke & CO alarm kidde kn copp b lpm battery carbon monox
Frequently Asked Questions
Does the SMCO600NV-AC detect both smoke and carbon monoxide?
Yes. It is a combination alarm that senses both smoke from fire and carbon monoxide (CO) gas in a single hardwired unit, so one device covers two hazards in a room.
Is this alarm hardwired or battery powered?
It is hardwired to your home's 120V AC circuit and includes a battery backup that keeps the alarm working during a power outage. It is not a plug-in or standalone battery unit. For non-wired rooms, choose a plug-in model like the SMCO100V-AC.
Can I interconnect it with my other alarms?
Yes. The SMCO600NV-AC is interconnectable with compatible First Alert and BRK hardwired alarms. When wired in a series, a hazard detected by any one unit sounds every connected alarm in the home.
What does the SC5 designation mean?
SC5 refers to First Alert's smart combination alarm series for this model. We list only the specifications the manufacturer publishes; if a feature is not stated on the product, we do not claim it.
Does it use a photoelectric or ionization smoke sensor?
First Alert does not publish the sensor technology for this model, so we do not state one. Photoelectric sensors respond faster to smoldering fires and ionization to fast-flaming fires; confirm with the manufacturer if sensor type is decisive for you.
Where should I install a combination smoke and CO alarm?
Install on every level of the home and near every sleeping area. Because carbon monoxide mixes evenly with air, mounting height is flexible. See our CO detector placement guide for room-by-room layout.
Why do I need a CO alarm if I already have smoke alarms?
Carbon monoxide is colorless and odorless, so you cannot smell or see it. A smoke alarm alone will not detect CO. A combination unit like this adds CO sensing without a second device.
How long does this alarm last before replacement?
Replace the entire unit at the end-of-life date printed on the housing. CO sensors typically last about 5-10 years and smoke sensors up to about 10 years, so combination units are replaced as a whole rather than by swapping one sensor.
Will it still work during a power outage?
Yes. The battery backup keeps the alarm active when 120V AC power is lost. Keep the backup battery fresh per First Alert's maintenance schedule so protection continues uninterrupted.
How do I test the alarm after installation?
Press and hold the test button until the alarm sounds, and test interconnected units to confirm they all respond. See our guide on how to test a smoke and CO alarm for the full routine and recommended testing frequency.
Is this a good replacement for my old hardwired alarm?
Yes, if your home is already wired for hardwired or interconnected alarms. It uses standard interconnect wiring and serves as a drop-in upgrade. Confirm your existing harness and connector are compatible before swapping.
Can I use this in a garage or workshop?
It is intended for living spaces. Smoke sensing is not rated for dusty or dirty garages, and for industrial gas exposure you should use a multi-gas meter such as the Forsensal 4-gas detector rather than a residential alarm.
Written by Steven Eaton, WC Safety Editorial. Specifications sourced from First Alert published data. Compare the range in carbon monoxide & smoke alarms.
WC Safety is an independent PPE retailer and Amazon Associate; no paid placement. Match the product to your specific hazard and follow your site PPE program.
Brand / Vendor
First Alert
Model / SKU
SMCO600NV-AC
Product Type
Smoke Detector
Condition
New
MPN
SMCO600NV-AC
Price
$129.98 (Amazon)
Rating
3.12 / 5 — 8 reviews
Availability
Check current availability on Amazon
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Verified Buyer Reviews
Customer Reviews
★★★☆☆3.1 / 5· 8 verified reviews
★★★☆☆
Feels a few steps backward from Nest Protect (Gen 2) but easy replacement.
6x as a nest protect replacement - doesn't seem worth the value. One false alarm within 2 weeks of installing that cleared itself. Very much not within expectations of the product's premium price. As the replacement product, at similar price (10+ years after the nest protects gen 2s) it should feel like these improve that design, but they feel like a few steps back in product quality, features. and customer experience. (no soft night light, no gentle reminder that things are good when the lights turn off, CONSTANT LED green light to show status). It feels like going from thoughtful design to much lower-effort, while paying the same price, 10-years later.
Anonymous · 2026-04-30 · ✓ Verified Buyer
★☆☆☆☆
Regret Purchase: Unreliable Smart Features and Design Concerns
I replaced 9 Nest smoke/CO detectors that were reaching end-of-life with these newer UL 9th edition units. While the underlying detection standards may be improved, the overall experience has been disappointing.
Anonymous · 2026-04-30 · ✓ Verified Buyer
★★★★☆
Good Nest replacement despite not having night light.
This worked great as a Nest smoke alarm replacement. It uses the Nest mount so there is less work to do to switch it over. It does not have the night light like the Nest so that was a negative about it.
Anonymous · 2026-04-30 · ✓ Verified Buyer
★☆☆☆☆
Save money and lots of frustration. THIS IS A DEFECTIVE PRODUCT -- DO NOT BUY.
Terrible product - I purchased 4 of these (3 wired, 1 battery) for my house because I had to replace Nest Protect. The product is cheaply made and difficult to mount to its base properly. The main problem is that it is prone to false alarms in the middle of the night. My master bedroom unit did this twice. Then I replaced it. Then the basement unit did this. Then the bedroom unit replacement unit (this purchase) did it. All in the space of several months. The alarms sometimes cannot even be silenced - the app responds "too much smoke cannot silence" even though there is no sign whatsoever of any smoke. The only way to stop it is to wait. Eventually it will let you silence it. Then it usually starts up a few times after that but eventually stops. If you look at reviews for this product this seems to happen to many people who get them. It is clearly a defective product. A good idea, but poorly implemented. Even if it worked properly, it is a big step down from Nest protect. Ugly, flimsy and no night light, no self test or any other amenities Nest protect had. Also, it claims to be compatible with Google Home, but you have to connect it to Google Home through its own app (and not a great app at that) - so one more account, one more app crowding your phone, additional complexity. If I could give this zero points I would. STAY AWAY!!!!
Anonymous · 2026-04-30 · ✓ Verified Buyer
★★★★★
Works Great with Protects
I have a house full of Nest Protects (8 in total), the first half of which started to age out, as they only last 10 years. Since the Protect was discontinued, I had to look elsewhere. Deciding on a replacement was difficult, as frankly, every available option has its detractors/horror stories in the reviews. Ultimately, however, I threw caution to the wind and ordered 4x of the hardwired SC5s.
Anonymous · 2026-04-30 · ✓ Verified Buyer
★☆☆☆☆
Absolutely horrible system -- DO NOT BUY
Absolutely horrible. I have a large house so I needed seven of these detectors. They connect via WiFi and use the First Alert by Residio App to monitor. All good, right? How wrong you would be! I cannot express how much I hate these units. They false alarm on nearly everything. Dusty house on a windy day. ALARM. SMOKE DETECTED. Drywall dust because you're adding an outlet? ALARM. SMOKE DETECTED.
Anonymous · 2026-04-30 · ✓ Verified Buyer
★★★★★
First alert hardwired SC5 wifi and 6 hardwired non wifi smoke detector set
Set up a single SC5 with compatible non wifi hard wired smoke detectors and also bought the quick connect adapters. Install was a breeze, and if you read the instructions BEFORE you jump in the app and set up were quick and easy.
Anonymous · 2026-04-30 · ✓ Verified Buyer
★★★★★
Rocket science mumbo jumbo.
It needs a default mode with no rocket science mumbo jumbo. I'm starting to get tired of discontinued products at my Google Home. They just kill themselves. The lifesan is short. Many versions did not wok. I hope it is better with this one. So far so good it is blinking. A temporary instalation code for a handiman would help.
Anonymous · 2026-04-30 · ✓ Verified Buyer
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