Yes, do what wolfchild said. With a mini-pump, you'll soon decide when you have "enough" air. You don't say what size your tires are, but if they are in the size range of most commuting bikes (32-40) you should be able to run pressures as low as 50 psi safely. Check and pump up further when you get home. If you're using narrow tires (23-25) higher pressures are necessary to prevent pinch flats.

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