<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><a href="https://support.rollsbattery.com/en/support/solutions/articles/816-hydrogen-off-gas-ventilation#:~:text=Through%20calculations%20we%20can%20show,oxygen%20must%20also%20be%20removed.">https://support.rollsbattery.com/en/support/solutions/articles/816-hydrogen-off-gas-ventilation#:~:text=Through%20calculations%20we%20can%20show,oxygen%20must%20also%20be%20removed</a><div><br></div><div><div dir="ltr"><div>I have seen this twice in the last 50 years in communications buildings. The above link explains the theory but we never identified the cause. Our assumption was a faulty charger but they were dead when we found the problem sometime after the event. What is the switch on the generator on the right side of the picture? Is it possible it created a spark?</div><div>Mark</div><div>Nashville</div></div><blockquote type="cite"><div dir="ltr"><span></span><br></div></blockquote></div></body></html>