Honestly, there is no need to worry about getting formaldehyde from burnt cotton.
It's hardly as bad as the media would have you believe.
http://www.formaldehydefacts.org
All organic life forms--bacteria, plants, fish, animals and humans--make formaldehyde at various levels. Formaldehyde does not accumulate in the environment or within plants, animals or people, as metabolic processes quickly break it down in the body and the atmosphere.
American Cancer Society -
http://www.cancer.org/cancer/cancercauses/othercarcinogens/intheworkplace/formaldehyde
Formaldehyde is normally made in the body. Enzymes in the body break down formaldehyde into formate (formic acid), which can be further broken down into carbon dioxide. Most inhaled formaldehyde is broken down by the cells lining the mouth, nose, throat, and airways, so that less than a third is absorbed into the blood.
Lab Animal Studies:
Exposure to formaldehyde has been shown to cause cancer in laboratory test animals.
In rats, inhaled formaldehyde was linked to cancers of the nasal cavity and leukemia. In one study of rats given drinking water containing formaldehyde there was an increase in stomach tumors, while another showed no increase in any kind of tumor or cancer.
In mice, applying a 10% solution of formaldehyde to the skin was linked to quicker development of cancers caused by another chemical.
Studies in people:
In one study, inhaling formaldehyde at levels at a concentration of 1.9 parts per million (ppm) for 40 minutes did not increase blood levels of formaldehyde.
Several epidemiology studies of people exposed to formaldehyde in the workplace have reported a link between formaldehyde exposure and
cancer of the nasopharynx (the uppermost part of the throat), but this outcome has not been observed in other studies. These studies looked at workers in occupational setting that use or make formaldehyde and formaldehyde resins, as well as at people who work as embalmers.
Studies of people exposed to formaldehyde in the workplace have also found a possible link to
cancer of the nasal sinuses.
Several studies have found that embalmers and medical professionals that use formaldehyde have an increased risk of
leukemia, particularly myeloid leukemia. Some studies of industrial workers exposed to formaldehyde have also found increased risks of leukemia, but not all studies have shown an increased risk.
Studies looking at the link between workplace exposure to formaldehyde and other types of cancer have not found a consistent link.