So ive been talking to a few people about putting a red top in my car (relocated my battery to the hatch I have rear seats) and I emailed optima and asked if it was ok to use it inside a car and heres what they said hope this helps anyone;
Hello

When used with a properly regulated constant voltage charging system (such as an alternator), the OPTIMA will not emit hydrogen gas. However, gassing can occur when charging at excessive voltage levels or in extreme high-temperature conditions. In automotive applications, this typically will not happen if the alternator/regulator stays below 15 volts.

It is important that*ANY*lead acid battery has proper ventilation. *ALL lead acid batteries can vent gas. *Traditional wet batteries do this immediately when recharged since they are not sealed. **Sealed lead acid batteries like Optima and all other “Dry Cell” batteries have safety release valves that will only vent if they are seriously overcharged. *Under normal operating conditions an Optima will not vent gas.**Since alternators or chargers can fail, the safest and correct mounting method for trunks and passenger compartments is to make sure that any possible gas venting will escape to the outside of the vehicle. *All vehicles with original equipment battery locations in trunks or passenger compartments will have a vent provision that should be used. *If you are custom mounting a battery in the trunk or passenger compartment we recommend venting the battery to the outside of the vehicle also. *

Thank*you,Tiara*Optima*Customer*Service