_Charging Precautions_ It is advisable to observe the following
precautions when charging a battery at home or elsewhere. During the
charging and for a short time immediately thereafter, the chemical
reaction in the battery gives off hydrogen gas in sufficient quantities
as to be explosive. When working near a battery being charged, or just
after it has been charged, it is important that no flame or spark have
an opportunity to ignite the hydrogen gas. To prevent possibility of a
static electricity spark’s causing such an explosion with the battery in
the car, it is well to ground the car electrically by means of a metal
bar or chain running from the car’s frame or bumper to the ground. When
the charging or recently charged battery is out of the car, it should be
placed where it will not be exposed to flame, spark, or static
electricity.