Replacing an RV propane and carbon-monoxide alarm means matching the alarm type, 12-volt power, front housing, wall opening and mounting style. MTI Safe-T-Alert offers compact surface models, flush-mounted rectangular and square models, and low-profile versions with trim rings. This illustrated guide compares the 25, 35, 45 and 85 series without assuming every alarm fits the same opening.
Four common dual-gas alarm housing styles
First identify whether the old detector sits on the surface of the wall or inside a recessed cutout. A trim ring can hide existing screw holes, but cannot make the electrical and cutout requirements of a new alarm universally compatible.
25-741 surface / 25-742 flush
35-742 long flush alarm
45-742 square housing
85-741 universal trim ring
Safe-T-Alert dual propane/CO size and mounting chart
| Model family | Mounting style | Manufacturer size / check |
|---|---|---|
| 25-741-BL / WT | Compact surface | 3½″ W × 2½″ H × 1¼″ D case; mounting bracket adds approximately ¼″ depth |
| 25-742-BL-TR / WT-TR | Compact flush, with trim ring | 7″ W × 4″ H × 1¼″ D with ring; manufacturer-listed cutout 3¼″ W × 2½″ H |
| 35-742-BL / BR / WT | Rectangular flush | 6⅜″ W × 2⅞″ H × 1¼″ D case |
| 45-742-BL | Square flush | 4¾″ W × 4¾″ H × 1¼″ D case |
| 85-741-BL-TR / WT-TR | Low-profile, trim-ring | 7″ W × 4″ H × 1″ D with outer ring; cutout must be checked separately |
These manufacturer-listed families use 12V DC hardwired power and provide both propane and CO warning functions. BL, WT and BR distinguish catalogued black, white and brown housings. Colour alone does not establish identical wiring, fit or available stock.
What to check before upgrading an older LP alarm
Read the complete MPN and date label on the old detector. Check whether it warns for propane only or for propane and carbon monoxide together; then identify the mounting style, case depth, wall opening and available 12V connection. For any replacement, verify sensor location according to MTI instructions, especially when replacing an alarm originally designed around a different housing.
Some older propane detectors interface with a separate LP-gas shutoff valve or control relay. Standard dual-gas detectors should not be assumed to provide that same function. Check the exact approved alarm and relay configuration with a qualified RV technician rather than bypassing an existing valve circuit.
MTI states that Safe-T-Alert gas alarms have a five-year service life. Follow the factory replacement date and model-specific instructions; an alarm that still powers on is not necessarily an acceptable replacement for an expired sensor. If an alarm sounds, leave the RV and seek assistance from a safe location rather than trying to diagnose a leak indoors.
Find matching dual-gas alarm product photos
Use these actual UsedRVParts catalog items to compare model markings, colours and faceplate layouts. Some inventory may be zero or the listing may be a new replacement part rather than used stock. Open the product to check condition and availability; viewing or pickup, where available, is by appointment in Kelowna.
