We are using about 10 115ah wet lead acid batteries to provide electricity for our business in the field. At night, we charge them all in the same space. The space does have a bit of airflow, but it's not like we are leaving a window open. Is charging this many batteries together in close proximity safe? I am asking due to the gases that are given off by them all while charging. Thank you for your help!
Is it an enclosed space? Of what size? How much is "a bit of airflow?" Is there a vent or two? How big?
Lead-acid cells give off hydrogen gas when charging, which can be very explosive and even dangerous to breathe. Is there anything nearby which could spark and ignite it? (Light switch, faulty wire, sparks from grinder, etc.) They also get warm, so need some convective airflow to stay cool. Excessive heat shortens their usable service life greatly.
Essentially, if these are all crammed into a tiny space with no ventilation, then it's asking for trouble. Like this: https://www.youtube.com/watch?v=d_TnsHu2u4c
The regulations that apply to this scenario will vary from one country to another, and from one scenario to another (domestic, commercial, industrial). I strongly recommend you find out what applies in your location & situation.
Forced air extraction AT THE ROOF LEVEL is highly recommended, as lead-acid batteries WILL vent significant amounts of H2 (qty depends on many factors), and it will pool at ceiling level & work downwards, displacing ordinary air. Concentrations of as little as a few percent become explosive.
As @rtdsc said, how much H2 depends on many variables, including charge profile, battery types, temperature, etc. Also an acid-resistant 'drip tray' for all the batteries to sit in would be a good idea.
The proximity of the batteries to each other isn't so much of an issue from a H2 gas perspective, but it can be in terms of cooling - lead-acid doesn't like heat, & giving them as much space between them (i.e. a few inches) is ideal.
Typical standards require hydrogen concentration less than 1-2%: On the description you've given, that would require a complete air change every week or so, and you probably have a complete air change several times an hour.ventilation requirment guesser
Note: Hydrogen is flammable, but difficult to ignite, at 4%. Explosive at 18% safety sheet