Physical characteristics of three respirable samples of Montserrat volcanic ash (M1, M2, and M3), DQ12 quartz, and TiO2
| Particle | Surface area (m2/g) | Cristobalite content (%) | Proportion of particles <3 μm in diameter (%) |
| M1 | 6.59 | 2.5 | 91.8 |
| M2 | 7.94 | 11.1 | 86.4 |
| M3 | 5.89 | 5.8 | 86.2 |
| DQ12 | 10.10 | Not measured | 99.9 |
| TiO2 | 6.68 | Not measured | 100 |