First Alert HD6135FB Hardwired Heat Alarm
- 135 F fixed, or a rise of more than 15 F in one minute
- 120-volt AC hardwired, 9-volt battery backup
- 85-decibel siren
- Interconnects with 12 First Alert or BRK hardwired alarms, plus 6 other devices
- Household remote can test and mute it, remote sold separately
- Latching indicator shows which unit triggered
Last refreshed Sep 8, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A smart heat alarm for crawl spaces, laundry rooms and garages, combining fixed temperature and rate-of-rise sensing with remote muting. It needs hardwiring, and the warranty term is not stated.
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ASIN: B000Q6LXW2Model: HD6135FBCategory: Smoke Detectors & Fire Alarms
Overview
First Alert pairs a fixed temperature sensor with rate-of-rise detection in this hardwired heat alarm, so it reacts to both high heat and a fast climb. A microprocessor screens out false alarms, and a backup battery runs it through power cuts.
Rate-of-rise sensing is the standout, catching a fast-growing fire before the room reaches the fixed trip point. It must be wired into household power and only links with First Alert or BRK hardwired units.
Who it's for
Homes with First Alert or BRK hardwired alarms get heat coverage in spaces too dusty or humid for smoke alarms. Owners of other brands of interconnected alarms should match their existing system.
Pros and cons
- Detects both high heat and fast rise
- Microprocessor reduces false alarms
- Mute or test with a TV remote
- Latching indicator finds the source unit
- Warranty term not stated
- Interconnect limited to First Alert and BRK
Performance notes
Response comes from two triggers: a fixed heat threshold and a rate-of-rise check that alarms on a sharp temperature jump within a minute. The microprocessor filters short spikes to cut nuisance alarms, and the latching indicator points to the unit that started a network alarm.
Specifications
| Brand | First Alert |
|---|---|
| Model | HD6135FB |
| Dimensions & fit | |
| Item weight | 7.04 ounces |
| Item Dimensions D X W X H | 2"D x 2"W x 2"H |
| Capacity & performance | |
| Upper Temperature Rating | 135 F, or rise over 15 F in one minute |
| Power & efficiency | |
| Power Source | 120-volt AC, 9-volt battery backup |
| Construction & materials | |
| Enclosure Material | Plastic |
| Color | White |
| Compatibility & installation | |
| Compatible Devices | Up to 12 First Alert or BRK hardwired alarms, 6 other compatible devices |
| Mount type | Wall or ceiling |
| Included components | |
| Unit Count | 1 Count |
| Warranty & support | |
| Manufacturer Warranty Description | Warranty |
| Other details | |
| Sensor Type | Fixed temperature and rate-of-rise |
| Alarm | 85 decibels |
| Remote control | Most household remotes, sold separately |
| Features | Test/silence button, latching alarm indicator, battery drawer, mounting bracket |
| BuiltIn Media | 1 pk |
| Item Highlight | HD6135FB, 9V Battery Backup |
| Item Type Name | GAS_SMOKE_FIRE_ALARM |
| Product Style | Heat Alarm |
Frequently asked questions
How do I change the battery in the First Alert HD6135FB?
It has an easy-access battery drawer for the 9-volt backup battery, so the unit does not need to come off the bracket.
Where should the First Alert heat alarm be installed?
The description names crawl spaces, laundry rooms, garages, kitchens and other areas where smoke alarms are not an option, on a wall or ceiling.
Does the First Alert HD6135FB come with a remote?
No. It works with almost any household remote control, which is sold separately.
Is the First Alert HD6135FB a smoke alarm?
No. It senses heat and temperature rise only, for spaces where smoke alarms are not suitable.