Battery rooms or stationary storage battery systems (SSBS) have code requirements such as fire-rated enclosure, operation and maintenance safety requirements, and ventilation to prevent hydrogen gas concentrations from reaching 4% of the lower explosive level (LEL). Code and regulations require that LEL concentration of hydrogen (H2) be limited to 25% of LEL or 1% of room volume. The room ventilation method can be either forced or natural and either air-conditioned or unconditioned. Battery manufacturers require that batteries be maintained at 77ºF for optimum performance and warranty. This article will look into the battery room ventilation requirements, enclosure configurations, and the different ways to accomplish them.