>>513437417
Yes, it can. It's called CO spiking. It can be done by injection or by the vacuuming process itself by removing more of the lighter gassed like nitrogen than it does the heavies gasses like those containing carbon. The CO and even some CO2 will remain and over time will fill the less dense pockets vacated by nitrogen and even slightly heavier molecular oxygen.

But here is a case where CostCO was caught improperly packaging it in concentration too low to be effective or from a leak in the packaging. Don't ever say CostCO doesn't use CO ever again.