The restrictions to be met for playing a card are always clear when referring to temperature; they either say "temperature below or equal to X degrees" or "above or equal to X degrees". However, when the restriction is on oxygen level, we have only found cards explicitly saying "below or equal to X% level", but none explicitly stating "above or equal to X% level". We therefore have the doubt on how to interpret the restriction for those that state only "X% level". Does it mean the card can only be played when the oxygen level is that "exact X% level"? Or can it be played when it is "X% level or above"? Thanks!
It's a minimum.
From the designer (on this post):
All maximum requirements have a 'max' in the requirement box and have a red background color in the box. All other requirements are minimum requirements (and should have been explained as such) and have a yellow background color in the requirement box. Most requirements are of the 'minimum' type, so we thought it would clutter up the cards too much to have a 'min' there. 'Minimum' is, after all, the most natural type of requirement.
It is "X% level or above".
The rulebook gives a few examples of cards, along with the restrictions of when they can be played. Card "D" in the example list is Livestock, which shows "9% oxygen as a requirement", and the rules state:
To play card D, the oxygen level must be 9% or higher. You also need to have plant production, since the card requires you to decrease your plant production.
Card E is Shuttles, and it shows the same requirement icon, needing 5% oxygen. The rules state:
Card E requires 5% oxygen and energy production.
So the rules consider "requires x% oxygen" to be interchangeable with "requires x% oxygen or more".