Air quality in an area of Port Richmond is improving after a Thursday fire, but was not back to normal early Friday afternoon, city officials said. They advised residents to continue being cautious but said they “otherwise can return to their normal routines” after being told to stay inside Thursday evening.

Residents in the area of the fire, which occurred at Wheatsheaf Lane and Richmond Street, should take heed of the temporary drop in air quality, particularly those who have chronic health conditions, the city said.

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The city’s air quality monitor south of the fire is measuring normal levels, and the monitor to the north was still measuring slightly elevated levels, the city said in a noon news release. Health officials expect the levels to return to normal “shortly” but recommended caution for people with breathing or heart problems.

Exposure to particulate matter can exacerbate conditions such as asthma and heart disease, posing a risk to people with such medical conditions, children, and the elderly. Poor air quality can also cause irritation, coughing, shortness of breath, and other short-term symptoms.

The fire occurred late Thursday afternoon at a scrap-metal business, sending up huge billows of smoke. It was declared under control at 5:35 p.m. Testing showed that no toxic compounds were identified in the air at levels that would threaten human health, the Philadelphia Department of Public Health said.

Air quality after the fire was worst Thursday between 5 and 6 p.m., when the health department told area residents to stay inside. Health officials reported elevated levels of particulate matter in the area overnight, but said the measurements were steadily improving.

The pollution didn’t affect the entire city. Philadelphia’s air quality was rated “good” on Friday, the best rating.