The Phoenix Brick Yard, operating south of downtown Phoenix for 67 years, is being pulled into the 21st century by air-quality regulations and some agitated activists.

The brick-making operation, at Seventh Avenue and Mohave Street, has been classified as a major source of hazardous air pollutants.

The plant is among the last batch of operations that Maricopa County is bringing under the umbrella of its permit that regulates major polluters.

A hearing is Tuesday. But emotions already are running high.

Maricopa County is proposing a permit that would allow the brickyard to emit an average of 287 pounds a day of hydrogen fluoride. That’s within the limit allowed by federal hazardous air-pollutant regulations.

But it’s too close for comfort for a group of south Phoenix community activists. Phoenix is uneasy about the proposal, too, arguing that the allowable emissions are very close to the federal limit.

Hydrogen fluoride is a byproduct of the baking process that converts clay into brick. In its gas form, it can irritate the eyes and respiratory system, creating a burning sensation. In acute exposures, it can cause swelling in the lungs.

Local residents have complained about odors, said Gaye Knight, environmental programs specialist with Phoenix.

But Frederic Campbell, president of Phoenix Brick Yard, said many of those complaints have been misplaced. He said a city sewer project was the source of recent odors, not his plant.

And county records show only six resident complaints were filed in the past five years.

In the neighborhoods around the plant, residents on a recent weekday shrugged when asked about the plant’s effect.

Lupe and Theresa Mendez said the brickyard is unobtrusive.

“If it was loud and had a smell, then it would be a problem,” said Theresa, who lives a half-block west of the plant.

Lupe, who has lived in the area all his life, has sentimental attachments to the plant. “It’s actually history for me,” he said. “I’m 36 years old, and I enjoy looking at it.”

But Ethel Lane said she almost immediately had problems when she recently visited a friend who lives across the street from the plant.

“I experienced a strong odor,” Lane said. “It tickled my nose, my eyes started running and my throat started tickling.”

Steve Brittle, an activist with Don’t Waste Arizona, said he got a severe headache after distributing fliers opposing the permit.

Brittle argues that the plant’s emission should be subject to stricter controls that the U.S. Environmental Protection Agency has proposed for hazardous pollutants. Those would cut daily emissions by 95 percent, most likely through the use of scrubbers on the plant’s smokestacks.

However, those standards are not in force, said Steve Peplau, the county’s air-division manager. And the brickyard will keep within existing limits by agreeing to cut back daily production a bit, to 9.9 tons of clay per hour, instead of the usual 10 tons.

City officials want county regulators to require hourly records on the hydrogen fluoride emissions to more accurately track what neighbors are exposed to. They also want the county to ban the use of a “rain cap” on the smokestack of the brickyard’s kiln, since the cap has the effect of forcing emissions to be released horizontally, where they are in more immediate contact with neighbors.