One volunteer described the experience as an "opportunity of a lifetime" and "beyond exciting".
Footage shows emergency vehicles outside a Sainsbury's where people are reporting breathing difficulties.
By Simon Stone
BBC Sport at Villa Park
By Michele Paduano
BBC Midlands health correspondent
Birmingham's famous city centre fountain restored as part of £25m scheme.
By Sophie Madden
BBC News, West Midlands
CCTV footage shows Mohammed pawning a stolen bracelet and using a bank card after killing pensioner David Varlow.