The Bureau of Meteorology says south-easterly winds have caused smoke to drift across Perth.
People concerned about smoke in the air could be assured there were no major bushfires burning, assistant chief operations officer Bruce Jones said last night.
"If a major fire endangers life or property, FESA (Fire and Emergency Services Authority) issues alerts through the media and via the internet," Mr Jones said.
"The smoke has been generated by burn-offs on land managed by the Department of Environment and Conservation and the current haze will linger until stronger winds blow it away."
The smoke has been caused by smoldering from two prescribed burns carried out by the DEC on Thursday and Friday as well as other burns being undertaken by private landholders east of Perth.
People with health issues exacerbated by smoke are asked to follow the advice of their health practioners and stay indoors.
The DEC said it continued to undertake prescribed burning to achieve community and biodiversity protection objectives.
Mr Jones said that when smoke haze occurred the FESA Communications Centre tended to receive many calls from the public on its emergency triple-zero line.
"FESA Communications Centre call-takers receive triple-zero calls and quickly despatch fire and emergency responders to extinguish fires, perform life-saving rescues and minimise damage to property and the environment," he said.
"It's important that people only call triple-zero to report a fire and in life-threatening emergencies.
"When people ring in about burn-offs they can tie up the triple-zero call-takers and possibly even cause lives to be put at risk."