Explosion-proof vacuums are made of metals such as stainless steel and aluminum that allow for conductivity, helping to prevent a build up of static. Static could create a spark if it jumps to a lesser-charged service. This is called arcing.
These vacuums are also designed with conductive wands, brushes and wheels. Built-in bumpers help eliminate metal-to-metal contact.
For extra safety, janitors should not pick up materials the vacuums are not intended for and watch out for lit cigarettes or hot pieces of metal in grinding areas.
posted on 6/17/2010