Enter project details
Example data table
| Scenario | Inputs | Estimated detectors |
|---|---|---|
| Single-family, two levels | Levels: 2, Sleeping areas: 1, Bedrooms: 3, Garage: Yes, Fuel: Yes, Bedroom units: Yes | 2 + 1 + 3 + 1 + 1 = 8 |
| Apartment unit, one level | Levels: 1, Sleeping areas: 1, Bedrooms: 2, Garage: No, Fuel: No, Bedroom units: No | 1 + 1 = 2 |
| Small commercial suite | Type: Small commercial, Levels: 1, Area planning: 3,600 sq ft @ 900 sq ft | Minimum 2, plus area add-ons ⇒ 4 |
Formula used
This calculator estimates the detector count using a practical planning model. It starts with a base unit on each level, then adds units around sleeping spaces, and optional units for bedrooms, mechanical spaces, and garage entry points.
- Per level:
Units_level = Levels - Outside sleeping areas:
Units_sleep = SleepingAreas - Bedroom units (optional):
Units_bed = Bedroomswhen enabled - Optional add-ons: mechanical room, garage entry, basement extra
- Area planning (optional):
Units_area = ceil(TotalAreaSqft / CoverageSqft), thenAdd = max(0, Units_area − Levels) - Total:
Total = Levels + SleepingAreas + BedroomUnits + AddOns + AreaAdd
Always verify placement, interconnection, and device type requirements with local regulations and manufacturer instructions.
How to use this calculator
- Select your project type to set a reasonable minimum count.
- Enter the number of levels, including basements if present.
- Enter sleeping areas and bedrooms for residential planning.
- Toggle fuel appliances and attached garage if applicable.
- Choose optional additions like mechanical room or basement extra.
- Enable area-based planning if you need density for large spaces.
- Click Calculate to show results above the form.
- Use the CSV and PDF buttons to save your estimate.
CO sources and risk zones
Carbon monoxide forms when fuel burns incompletely. Common sources include boilers, water heaters, fireplaces, generators, and vehicle exhaust from attached garages. Risk increases where combustion equipment shares air with occupied rooms, ventilation is weak, or people sleep. This calculator separates bedrooms, floors, and special zones to prioritize higher consequence areas. CO is odorless, so placement and coverage matter.
Typical detector placement logic
Count planning typically covers sleeping areas and every level, including basements. Bedrooms and nearby corridors often justify one unit per sleeping wing, plus one on each story. Long corridors, open plans, and mixed occupancies may need extra units to avoid dead zones. Area based spacing offers a conservative way to scale counts for larger footprints. Use the area option when rooms are wide.
Interconnection and audibility planning
Many projects choose interconnected alarms so activation anywhere warns occupants everywhere. Interconnection helps when doors are closed at night, layouts are deep, or background noise is high. This tool estimates quantity, but you should still plan power type, wiring routes, and testing access. Verify audibility targets and notification requirements for the occupancy. Decide whether hardwired or wireless interconnect fits your scope.
Special areas: garages and mechanical rooms
Attached garages, mechanical rooms, and utility spaces can create localized CO peaks. Designers sometimes add a unit near the garage entry or near combustion appliances, while avoiding direct drafts, steam, and extreme heat. Basements with equipment or limited air change are often treated as separate zones. Use the optional toggles to reflect these needs without overcounting small rooms. Mounting height and airflow can change response time.
Using the estimate for procurement and inspection
An estimate supports purchasing, rough in, and inspection readiness. After calculation, document inputs using the export buttons and review assumptions. Compare results with local rules, manufacturer guidance, and the final floor plan. If layouts change, update levels, bedrooms, and area so the detector schedule matches as built drawings. Ordering a spare count can reduce change orders.
FAQs
Does this calculator replace code requirements?
No. It provides an organized estimate based on common planning rules. Always verify detector quantity, locations, device listing, and installation details against local regulations, the authority having jurisdiction, and the manufacturer instructions for the selected model.
Should I place a detector in every bedroom?
Some standards focus on sleeping areas and nearby hallways rather than every bedroom. If bedrooms are separated by doors or long corridors, adding units closer to each bedroom cluster can improve warning time and audibility.
How does floor count affect the result?
Each level increases the baseline because CO can migrate through stairwells and pressure differences. Basements often need coverage when they contain combustion equipment or have limited ventilation, so include them as separate levels.
When should I enable the attached garage option?
Enable it when a garage connects directly to the building or shares an air path. The calculator can add coverage near the entry point to address vehicle exhaust infiltration and short term peak exposure risks.
What is the purpose of the area based planning option?
It adds detectors based on total floor area, which helps for large open plans, commercial spaces, or unusually long corridors. Use it when a simple per level minimum feels too low for the footprint.
How accurate are the CSV and PDF exports?
They export the same inputs and results shown on screen. Use them to document assumptions, share with a team, and track revisions. If you update any inputs, export again so records match the latest estimate.