Three Garland firefighters were treated at Baylor hospital after inhaling chemical vapors on a hazardous material call.
The call came in Saturday night from a business on 1400 Wall Street.
Workers were attempting to discard a chemical, but inadvertently put it in a vat that already contained another chemical.
It sparked a reaction which created vapors in the area, leading to the evacuations of several businesses nearby.
The chemicals were allowed to self-extinguish, according to the Garland fire department.
The firefighters who breathed in the fumes were examined and released from the hospital.