Stop running fans 24/7. A good CO detector lets you run exhaust fans only when needed, keeping air safe and bills low. This practical guide shows you five proven, parking‑grade options—where they fit, and how to size, place, and maintain them.
Quick Picks (what we actually use)
- Macurco CM-6 — Stand-alone detector + controller. Digital display, buzzer, two relays (fan + alarm), 4–20 mA to BMS. Great for retrofits.
- Honeywell E3Point — Networkable. Swap-in cartridges (CO/NO₂), RS-485 (Modbus/BACnet), relays + buzzer. Ideal for larger sites and BAS.
- Conspec 911154-1 CO/VC — Built as a ventilation controller: LCD, 80 dB alarm, onboard relays, fail-safe.
- BAPI Digital CO (or CO+NO₂) — Rugged enclosure, analog or BACnet/Modbus outputs, field-replaceable sensor modules.
- ACI CO Room Series (CO-R) — Simple 4–20 mA / 2–10 V transmitter; optional relays/LCD. Cost-effective for distributed points.
Best CO Sensors -BuildMEP verdict :
- Small/medium garage or retrofit → Macurco CM-6.
- Large garage with BAS → Honeywell E3Point (add NO₂ if diesel present).
- “Wire-and-go” fan control → Conspec CO/VC.
- Harsh areas / mixed fleets → BAPI CO or CO+NO₂.
- Budget transmitter points → ACI CO-R.
Specs that matter (at a glance)
| Model | CO Range | Local Alerts | Outputs / Comms | Why choose it |
|---|---|---|---|---|
| Macurco CM-6 | 0–200 ppm | Display + buzzer + 2 relays | 4–20 mA + relays | Fast retrofits; controller built-in |
| Honeywell E3Point | ~0–250 ppm | Display + buzzer + relay | RS-485 (Modbus/BACnet), 4–20 mA | Networked BAS, swap CO/NO₂ |
| Conspec 911154-1 CO/VC | Garage control range | LCD + 80 dB + relays | Fan/alarm relays | Purpose-built ventilation control |
| BAPI Digital CO / CO+NO₂ | up to 0–500 ppm | Optional LCD/relays | 0–10 V, 4–20 mA, BACnet/Modbus | Rugged; dual-gas option |
| ACI CO Room (CO-R) | 0–125 ppm (to 250) | Optional LCD/relays | 4–20 mA + 2–10 V | Simple, economical transmitter |
Placement & quantity (practical rules)
- How many sensors? Plan roughly 1 sensor per ~5,000 ft² as a starting point. Add units at ramps, pay booths, and dead-air corners. Adjust by airflow and layout.
- Mounting height: Breathing zone (≈ 1.2–1.8 m / 4–6 ft). Avoid direct fan jets and exhaust pipes.
- Zones: Split the garage into zones and control fans per zone for faster response and energy savings.
Quick formula:
Sensors (baseline) = ceil(Area ÷ 5,000 ft²)
Example: 60,000 ft² → 12 sensors baseline.
Setpoints & control (what inspectors expect)
- Typical triggers: Fans ON ≈ 25 ppm CO. If diesel vehicles are present, add NO₂ (common trigger ≈ 3 ppm).
- Staging: Use two (or more) stages or VFD speed ramps as CO rises.
- Fail-safe: Any sensor fault/power loss should command fans ON.
Tip: If you see buses, generators, or delivery trucks regularly, pick a CO+NO₂ solution (e.g., E3Point with NO₂ cartridge/remote or BAPI dual-gas).
Maintenance (keep it accurate)
- Bump test: Quarterly to semi‑annual.
- Calibration: Annually (or per local code/AHJ).
- Sensor life: Typically 2–5+ years; many units offer swap‑in cartridges/modules.
- Documentation: Label each sensor with ID and calibration date; keep a simple log for auditing.
Model-by-model notes (short & useful)
Macurco CM-6
- Best for: Stand-alone control without extra panels.
- What you get: Digital ppm display, buzzer, fan relay + alarm relay, 4–20 mA to BAS/VFD, selectable setpoints.
- Why pros like it: Mounts to a 4×4 box, quick to commission, ideal for retrofits.
Honeywell E3Point
- Best for: Large sites with BAS integration.
- What you get: RS-485 (Modbus/BACnet), relays, buzzer, plug-in CO/NO₂ cartridges, and a network up to many points.
- Why pros like it: Easy to expand or switch the diffgases later.
Conspec 911154-1 CO/VC
- Best for: “Wire-and-go” ventilation control.
- What you get: LCD, loud alarm, onboard fan relays, fail-safe behavior.
- Why pros like it: Minimal programming; made for garages.
BAPI Digital CO / CO+NO₂
- Best for: Harsh environments or diesel mix.
- What you get: Rugged enclosure, analog or BACnet/Modbus, optional dual-gas and field-replaceable modules.
- Why pros like it: Flexible options; replace the sensing module instead of the whole device.
ACI CO Room (CO-R)
- Best for: Budget-friendly distributed sensing.
- What you get: 4–20 mA + 2–10 V outputs (simultaneous), optional relays/LCD, room or duct versions.
- Why pros like it: Simple, widely stocked, works with any controller.
Buying Guide
Macurco CM-6 (Low-Voltage)
Check priceHoneywell E3Point (Base + CO cartridge)
Check price
FAQ
If you have diesel vehicles (buses, delivery trucks, standby gensets), yes—add NO₂. For petrol-only garages, CO alone is often accepted. Check your AHJ.
Sensors still help. Natural ventilation varies with wind; demand-control smooths the peaks and keeps alarms consistent.
Better to zone and stage. It reduces noise, hot spots, and energy use.
