With e-cigarettes becoming more popular, the TTC board will be debating whether to ban the use of the products from property.
Staff are working on amending a bylaw and commissioners are expected to vote on the matter in the fall.
"We have a responsibility to protect both our employees and our customers who ride the system," TTC spokesman Brad Ross tells Newstalk 1010. "E-cigarettes or vaping have become an issue in the last couple of years so we took a look at this."
Ross says there are still too many question marks surrounding e-cigarette vapour.
"The health ramifications, if you will, are still generally unknown."
He says that with more people using e-cigarettes, organizations and governments need to deal with them and have appropriate policies in place.
If commissioners approve a ban, the new rule would be in place in 2015.