Tecnobosque Wildfire Knowledge Graph · Smoke & Indoor Air
Reference Concept · v1.0Definition → relationship → calculation → evidence context
PM2.5 is airborne particulate matter with an aerodynamic diameter of 2.5 micrometres or smaller; wildfire smoke can contain high concentrations of these fine particles.
PM2.5 · fine particulate matter
What is pm2.5?
PM2.5 can penetrate buildings through leakage and ventilation. Indoor concentration can therefore remain elevated even when windows are closed.
Portable air cleaners and HVAC filtration can reduce indoor particle concentration, but their effect depends on airflow, filter efficiency, room volume, infiltration and ongoing smoke conditions.
Why it matters
Wildfire-smoke protection indoors is largely an exposure-control problem: reduce particle entry, avoid indoor sources and remove particles with filtration and air cleaning.
PM2.5 is a concentration of fine particles in air, commonly reported in micrograms per cubic metre. It is not the same thing as AQI, which is an index derived from pollutant concentration and health breakpoints.
C_PM2.5 = particle mass ÷ air volumeAmbient PM2.5 concentration is commonly expressed in µg/m³. Indoor concentration changes over time as outdoor particles enter, deposit, are filtered, or are generated indoors.
Particle mass concentration in a volume of air.
Air volume of the modelled indoor zone.
Ventilation or cleaner airflow affecting particle transport/removal.
Equivalent particle-free airflow delivered by an air cleaner.
Concentration versus index
A monitor reports a wildfire-smoke PM2.5 concentration of 40 µg/m³.
40 µg/m³ is a pollutant concentration, not an AQI number.To communicate AQI, apply the current EPA PM2.5 breakpoint interpolation.To model indoor exposure, use concentration directly in a mass-balance framework.Do not label 40 µg/m³ as “AQI 40.” Concentration and index are different quantities.
What controls or changes this quantity?
Higher outdoor smoke creates a stronger infiltration source.
Air exchange carries outdoor particles indoors.
HVAC and portable cleaners remove a fraction of airborne particles as air passes through them.
Cooking, candles and other combustion can add PM2.5 independently of wildfire smoke.
Engineering context
Ambient concentration measured or forecast outside.
Concentration inside a building or room.
Public communication index calculated from pollutant concentration.
Air-cleaning capacity used to reduce indoor particle concentration.
How to interpret it correctly
- Keep concentration units visible.
- Separate outdoor measurements from indoor measurements.
- Use time and location with any reported PM2.5 value.
- Do not treat one indoor sensor as representative of an entire building without considering mixing and placement.
Use the calculator as a transparent technical aid and keep its assumptions explicit.Open Indoor Wildfire Smoke PM2.5 Calculator →
Why it matters in wildfire analysis
During a smoke event, a cleaner-air room can have substantially lower particle concentration than outdoors if infiltration is limited and enough clean air is delivered.
Tecnobosque connects PM2.5 to AQI for communication and to CADR/ACH for engineering control of indoor smoke.
Limitations and boundaries
- Low-cost PM sensors can have bias and humidity sensitivity.
- A single-zone indoor model assumes well-mixed air and simplifies leakage and deposition.
- PM2.5 concentration alone does not describe every gas or pollutant present in wildfire smoke.
PM2.5 FAQ
What is PM2.5?
Fine particulate matter with aerodynamic diameter 2.5 micrometres or smaller.
How is PM2.5 measured?
It is commonly reported as micrograms of particle mass per cubic metre of air, µg/m³.
Is PM2.5 the same as AQI?
No. PM2.5 is concentration; AQI is an index calculated from concentration using pollutant-specific breakpoints.
Can indoor air cleaners reduce wildfire PM2.5?
Yes, if appropriately sized and operated, though building infiltration and ongoing outdoor smoke affect the achieved indoor concentration.