What function do the small holes or vents in the battery caps serve?

Question

DentroTest · Accepted Answer

During battery operation and charging (supplied by the alternator or an external charger), the chemical reactions between the sulfuric acid and the lead plates produce gases, mainly hydrogen and oxygen. If these gases were confined, the pressure build-up and their high flammability could cause deformation or even explosion of the casing. For this reason, the caps have ventilation holes that allow them to be released gradually and safely to the outside. These holes must in no case let out the electrolyte liquid, since it is a highly corrosive compound whose spillage would damage adjacent components.

What function do the small holes or vents in the battery caps serve?

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