I already thought of this... LiOH canisters would be what you need, but they are still hi-tech devices...
Else,
plants are an excellent things in that they convert CO² into O², provided they get enough natural light (smoke filters sunlight but is CO² rich, so they should be OK). If you have an aquarium, various species of algae (seaweed) are well known for their O² productivity. Near a window, they can probably get quite efficient.
For an optimal O² productivity, you can put the plants in the garden at night. Without light, they breath like any other living beings, and then produce (very little) CO². But even if you keep them inside the house, the O²/CO² balance is still very positive. The key is to provide them as much light, water, minerals & CO² as they need. High temperatures are an excellent thing too.
The only thing that could be hard to find is light. Artificial light (light bulbs) can help as "boosters". To know what exact wavelengths a plant needs, look at it's color. Most plants are green, which means they absorb the most everything between blue & red (UV), as seen below :
If you can find cheap UV lamps, that should work (keep away from these lamps though, UVs are bad for humans).
Also notice that plants need to rest. A plant which is exposed to light night and day perishes. But 6h should be enough for them to "regenerate" their cells (purge toxins).
So I would say that turning your house into an artificial jungle can be an answer, provided that the plants "sleep out" at night, and that they get enough natural & artificial light.
That won't fix the [ame="http://en.wikipedia.org/wiki/Carbon_monoxide"]
CO[/ame] problem though. CO is a poisonous gas because it fixes on the blood cells (hemoglobin) that usually carry O² throughout the body. The higher the concentration of CO, the less blood cells are available to carry O². Know that
protection devices exist, but they are probably not easily available.
Hope that can help...