Vapour blasting is just another word for wet blasting. Wet / Vapour blasting is the use of pressurized water mixed with abrasive, transported in a stream of air. The air, water and abrasive pressure can all be controlled independent of each other. This process gives a flushing action with the water so no media is impregnated into the substrate being blasted. 98 % of the dust is eliminated, no heat or hot sparks are generated. The abrasive and removed debris falls in close proximity to the blasted area. Very little abrasive is used with the process also. Because the media used is wet, the impact is much greater because the media is heavier and more powerful. It would be like getting hit in the face from wet sand compared to dry. This is why we can use way less pressure and media to do the same job.
Wet blasting is unlike dry blasting where the process is sheer force of media impact. With dry blasting there is a lot less control over the media and a lot more pressure is needed to create the same effect. Lots of media is just wasted in this process as the media is broken down easily along with the waste products of what is being blasted creating plumbs of dust and debris over a large area which can be carried far with the wind.