A new clan member and new Warframe gamer brought up a point that should be clarified and cleared up as knowledge for all – running and melee in survival missions DO NOT consume oxygen or life support. DE has long ago shot down this myth. The following link explains survival missions and is a very good source of information.
As the wiki states in the notes, life support drains 1% per every 1.5 seconds, which means it will take two and a half minutes to use up all 100%. You will improve life support by killing the enemy. Next time you are in a survival mission, take note of the percentage as you and your teammates slaughter everyone around you. The remaining percentage of remaining life support increases. Then take note when everyone is standing still waiting for the next wave to arrive. Life support will constantly decrease. Run around, jump up and down, act a fool. It will still decrease the same rate and amount.
The wiki also gives notes of how to play survival.
Stay together as a group. Try to locate an area where spawn rates of the enemy are frequent. An ideal point of activating life support is 60%, as each support only restores 30%. (Waiting until it is under 70 is good, as it takes three seconds to activate it. By that time you will hit the 60 mark.) The longer you survive, the longer it will take Lotus to send more life support.
Enemies spawn at spawning points where players can’t see, in rooms next to where players are. Big maps have more spawning points than small maps. Do not try to separate yourself from your team because it may disable the nearest spawning points and cause the enemies to spawn in other locations in greater numbers. Running could be used to help with spawning but do not run more than 3 room or spawn point would be random again.
It is not yet confirmed, but enemies appear to have a higher drop rate for secondary life support when killed in corridors. It is unknown whether or not this is dependent on the proximity to a primary life support drop, only that it appears to be this way.
As a side note – at 15 minutes and 35 minutes a key is rewarded. At 20 minutes a foundry item is awarded, such as a blueprint, a weapon part, etc.