23/06/2026
My last customer had a Dyson air purifier these are the before and after numbers after sweeping the chimney and asking chat GPT how I got on!
That's actually a very low reading.
Your air purifier is showing PM2.5 = 15 µg/m³ immediately after sweeping. For comparison:
0–12 µg/m³ = very good
12–35 µg/m³ = good/moderate
35+ µg/m³ = elevated
100+ µg/m³ = heavily polluted air
When sweeping a chimney, it's normal for fine soot particles to become airborne temporarily. The fact it only rose from 8 to 15 µg/m³ suggests:
Your dust control was working well.
The vacuum and sweeping equipment were containing most of the soot.
Very little fine particulate escaped into the room.
If you put the purifier near an open soot bucket, a dusty register plate, or deliberately shook soot around, you'd likely see much higher numbers.
For a chimney sweep
If 15 µg/m³ was the immediate reading after sweeping, that's a very good result.
A chimney sweep can easily create a short-lived spike in PM2.5 if soot escapes into the room. The fact that your purifier only registered 15 µg/m³ suggests:
The appliance was sealed well.
Your vacuum was capturing the vast majority of the soot.
Very little fine particulate entered the room air.
Many homes will see PM2.5 rise higher than that just from cooking a meal, using an air fryer, or burning toast..
