Tecnobosque Wildfire Knowledge Graph · Smoke & Indoor Air
Reference Concept · v1.0Definition → relationship → calculation → evidence context
Clean Air Delivery Rate (CADR) is the effective volumetric flow of contaminant-free air delivered by an air cleaner for a specified particle-size test, combining airflow with particle-removal performance.
CADR
What is clean air delivery rate (cadr)?
CADR provides a practical way to compare particle air-cleaning performance because it expresses the result as an equivalent flow of cleaned air.
For wildfire smoke, sizing should be based on the room volume, desired clean-air delivery and realistic operating speed. Multiple cleaners can contribute approximately additive CADR when used in the same well-mixed space.
Why it matters
CADR lets room volume and target air-cleaning rate be connected to practical purifier sizing during wildfire smoke.
A purifier can move a lot of air but remove particles poorly, or remove particles efficiently at a low airflow. CADR combines those effects into one useful clean-air quantity.
CADR ≈ η × QConceptually, CADR is the product of airflow Q and particle-removal efficiency η for the relevant test conditions. Published CADR values should be used directly when available.
Effective particle-free airflow.
Volumetric airflow through the cleaner.
Fraction of target particles removed per pass under the assumed conditions.
Indoor air volume used to relate CADR to ACH.
Sizing clean air for a room
A 40 m² room with a 2.5 m ceiling has a volume of 100 m³. A target of 5 clean-air changes per hour is selected.
Required clean-air flow = 100 m³ × 5 / hRequired CADR = 500 m³/hOne or several cleaners can be selected to meet or exceed that effective clean-air delivery.The target ACH is a planning assumption, not a guarantee of a specific indoor PM2.5 concentration.
What controls or changes this quantity?
Published CADR generally changes with fan speed.
Performance and airflow can change as filters load with particles.
Poor mixing can leave local zones with lower effective cleaning.
Outdoor smoke entering the room creates a continuing pollutant source that air cleaning must offset.
Engineering context
Effective clean-air flow delivered by the cleaner.
How many room volumes per hour are represented by a flow rate.
The pollutant concentration being controlled.
The geometric link between airflow and air changes.
How to interpret it correctly
- Use CADR for the relevant particle size / device rating when available.
- Size for the room actually being cleaned, not the whole building unless the system serves it.
- Account for noise and the fan speed people will realistically operate.
- Treat CADR as a removal capacity, not as a direct concentration forecast.
Use the calculator as a transparent technical aid and keep its assumptions explicit.Open Wildfire Smoke CADR Calculator →
Why it matters in wildfire analysis
During smoke events, creating one well-sealed cleaner-air room can be more practical than trying to clean an entire leaky building. CADR provides the engineering bridge between room size and air-cleaner capacity.
The Tecnobosque smoke tools connect CADR to ACH, PM2.5 and backup-power runtime for outage scenarios.
Limitations and boundaries
- CADR does not represent gas-phase pollutant removal.
- A well-mixed room assumption may not hold in large or partitioned spaces.
- Indoor concentration also depends on infiltration, deposition and indoor sources.
Clean Air Delivery Rate (CADR) FAQ
What is CADR?
Clean Air Delivery Rate is the effective volume of particle-cleaned air delivered per unit time.
Is CADR the same as airflow?
No. CADR incorporates particle removal as well as airflow.
Can CADR values from two purifiers be added?
As a planning approximation in the same well-mixed room, their clean-air delivery can often be summed.
How is CADR related to ACH?
ACH is CADR divided by room volume after converting to consistent time units.