oxygen masks
Again, I am no aviation expert, but I think in this situation, deployment of the masks is not a bad thing ( except from an economic viewpoint).
Firstly, with such thick smoke, there is considerable risk of passenger panic, with its safety impact. Many people associate oxygen with something that helps the body to survive. In this sense the presence of these masks can help allay anxiety.
Secondly, with such amount of smoke, there is a chance that some passengers with lung diseases such as asthma may get bronchospasm (tightening of the respiratory airways). In this situation, the extra oxygen may actually be of medical help.