Fig. 4 shows the effect of ambient air pressure on mean droplet size for PL = 1.0 MPa and PL = 4.0 MPa. The data for PL = 3.0 MPa are quite similar to those for PL = 4.0 MPa. The results show that under each certain pressure of water mist system, the mean water mist droplet diameter decreases with a decrease in ambient air pressure from 0.10 to 0.02 MPa, where as it Atomoxetine increases with a decrease in working pressure. This variation in the effect of the ambient air pressure on the mean diameter of water mist droplets is in partial agreement with the results reported by Wang and Lefebvre  and . The results obtained by Wang and Lefebvre showed that the Sauter mean diameter of a diesel-oil spray increased with an increase in ambient pressure up to a maximum value (i.e., 0.1–0.4 MPa) and then decreased with a further increase in Pa. The data reported in biosphere study may partially fill the gap in the literature data, especially for the cases of low ambient air pressure, i.e., Pa < 0.1 MPa.