It is now urging people driving in the area to take care and said those with medical conditions should avoid the smoke.
The TFS said it was not unusual for a hazard reduction burn to produce this much smoke.
It said fire fighters made every effort to reduce the amount of smoke but it was not always possible.
The Environment Protection Authority air quality rating shows the particle concentration in and around Hobart has reached nearly 190.
On a clear day it is five, and on a smoky winter's day can be around 50.
President of the Asthma Foundation of Tasmania Kevin Morgan said people with asthma should have been warned earlier.
"In an ideal world yes they should be warned as early as possible, so they can be prepared," he said.
"If this happens out of the blue and they're not prepared then it could have really nasty effects for a lot of people when they're not expecting it."
He said asthmatics could certainly be affected by this level of smoke.
"On these kinds of days they need to stay in doors, they need to make sure they've used their preventer medication and use their reliever medication.