Factors that influence the results of a study that the researcher did not, or could not, account for are known as

The answer to this question is Confounding variables
Confounding variables often created to the failure in control by the researchers that will eventually damage the validity of the research.
For example, if researchers are finding the correlation between tofu consumption and breast cancer, the gene that improve the chance of causing cancer could be considered as confounding variables.

Carbon monoxide is usually more dangerous indoors.