In recent years, there has been a marked increase in the deployment of lithium ion batteries in energy storage systems (ESS). Many ESS are being deployed in urban areas both in high rise structures and single- and multi-family residences. As the usage has increased so has the hazards to life and property if batteries are not stored or maintained appropriately. Li-ion cells are sealed units, and thus under normal usage conditions, venting of electrolyte should not occur. If subjected to abnormal heating or other abuse conditions, electrolyte and electrolyte decomposition products can vaporize and be vented from cells. Accumulation of liquid electrolyte is unlikely in the case of abnormal heating. Vented electrolyte is flammable, and may ignite on contact with a competent ignition source, such as an open flame, spark, or a sufficiently heated surface. Vented electrolyte may also ignite on contact with cells undergoing a thermal runaway reaction. Lithium Battery Safety PDF. Hazard Assessment of Lithium Ion Batteries can be found here.