Sleep your baby on their back
Sleep close to your baby
Do not use an old mattress
The longer a mattress has to break down and increase the amount of fungus inhabiting it, the greater the amount of gases.
If the theory is correct, I would think extra blankets and things could trap the gases rather than letting them disseminate as quickly as they otherwise would have, thereby increasing the risk. Also, some blankets and stuffed animals are even treated with these chemicals.
Do not smoke during pregnancy or after baby is born
Exposure to cigarette smoke in utero and secondhand is just bad for a baby in many ways, affecting much of their development, including their respiratory and immune systems.