Add some plants to your daytime environment to boost the oxygenation. Plants not only produce oxygen during daylight hours, they also act as a great natural air purifier for our stale indoor air by absorbing carbon dioxide, pollutants and other toxins.
Some great air cleaning houseplants are: Chinese Evergreen, Bamboo Palm, Aloe Vera, Spider Plants, Mums, Dumbcane, Golden Pothos, Ficus, Gerbera Daisy, English Ivy, Heart leaf philodendron, Janet Craig, and Peace Lily.
As a rule of thumb, allow one houseplant per 100 square feet of living area. The more vigorous the plant, the more air it can filter. Keep in mind that plants will not do much to alleviate tobacco smoke or dust in the air.