VSI raised the alert level to the third highest level Siaga (3 out of 4), because significant changes were observed at the crater lake. The most spectacular was the change of the lake water color to dark brown on 24 March.
In addition, a significant increase in CO2 concentration within 500 m from the Timbang crater was measured, from from 0.01% (by volume) in early March to 2.5% between 11 and 15 March. Also the emissions of the magmatic gas H2S increased. The now elevated gas concentrations are becoming a significant hazard (illustrated by a cat found suffocated by CO2).
Therefore, it is strongly advised not to approach the Timbang crater within one kilometer to avoid the risk of suffocation due to the high CO2 concentrations (note that CO2 is absolutely odorless and lethal when inhaled in larger quantities)