One cotton cloth

A clean white cotton square is hung by the stove. Exposed to the open fire, it turns grey with soot, and the change is visible to everyone. The smoke is no longer something you only cough from; you can see it caught in the cloth with your own eyes. That is the core essence of the intervention: the pollution becomes visible. No words, no literacy needed. Families take it home and hang it where they eat, a daily, visible reminder of what they have been breathing.

It doesn't filter or clean the air - it's exposed to the smoke and reveals it.

It is the smallest possible object doing the largest possible cognitive job: making an invisible harm visible enough to act on.

• Costs pennies, distributed with any existing cookstove programme.
• Culturally legible; sits alongside domestic textiles already in the home.
• Produces a physical, measurable signal researchers can score.