There are no reports of ill effects on the public from the fire at a wood recycling plant near Penistone, according to Public Health England.
But officials say people should continue to avoid smoke from the wood pile, which firemen have been tackling for five days.
A spokesperson for the health department watchdog said: “To date, there have been no reports of people experiencing ill effects from this fire.
“However, sheltering indoors provides protection from exposure to smoke, so we advise residents in any areas affected by smoke to continue to follow the advice from the emergency services; keep doors and windows closed as much as possible to limit any exposure to smoke.
“Motorists who have to travel through any smoke should keep windows closed, turn off air conditioning and keep their air vents closed.”
They said chemicals in the smoke could worsen existing respiratory conditions, such as asthma. People with asthma or other respiratory conditions should carry their inhalers and ensure they have taken any prescribed medication and keep it to hand.
“Any smoke can be an irritant and as such, if people need to be outdoors, they are advised to avoid or limit the time spent in areas affected by any smoke or ash,” the official added.
R Plevin, who operate the site, said to be the largest wood recycling plant in the UK, have promised an inquiry once the fire is under control.
It is the second fire at the plant, which makes fuel for power stations, in six weeks.