Vehicles of contamination help micro-organisms move from one place to another and hence can be a route for contamination.
Of the listed options, Blast Chillers are not vehicles of contamination. Blast Chillers are a bit like advanced freezers because they are used to freeze food at a fast rate. This ensures that food does not remain in the "<em>danger zone temperature of contamination</em>" - <em>period between temperature food is cooked at and temperature it cools at</em>".
As a result of this rapid freezing, items inside a blast chiller stand a way smaller chance of being contaminated as the low temperatures hamper bacterial growth.
