.."if the battery in a mechanical mod over-discharges and the device doesn't contain enough air holes to allow the battery to vent, there is a risk of explosion.".as of this month, there are 56 companies in china involved in the commercialization of car cell therapies. people who want to learn about and take action on the world�s biggest challenges. extreme poverty ends with you.. we have let patients down, admits senior northern ireland civil servant . april 2014 (15).