More than 60 Hanford workers have received medical exams for possible chemical-vapor exposure since spring.

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Three more Hanford workers reported smelling a suspicious, ammonia-like odor Thursday afternoon and received medical evaluations.

The workers were outside a facility where full air bottles are picked up and empty bottles dropped off after being used with supplied air respirators. Because workers were not inside the fence line of a tank farm, the respiratory protection was not required there.

No activities were going on in the area that would have disturbed waste, which increases the likelihood of chemical vapors being released, according to Washington River Protection Solutions, the Department of Energy’s tank-farm contractor. The vapors are associated with waste held in underground tanks.

Two of the workers reported symptoms. All three were released by medical professionals at the Hanford on-site medical provider to return to work.

The report of possible chemical vapors followed an incident Wednesday in which a portable instrument, called an area array unit, was set up in a tent for workers to change into protective clothing before entering the AX tank farm.

One worker told The Herald that an alarm that sounded on the unit was initially ignored and workers were told to continue putting on anti-contamination clothing.

About 10 minutes after the alarm sounded, workers were told to leave the change tent, and workers in the tank farm were told to leave, the worker said.

Tank-farm records indicate a report was made at 8:08 a.m. that an alarm within the tent was sounding. The instrument sends data in real time of measurements of ammonia and volatile organic compounds to a central Hanford location, where the data is monitored on a computer screen.

Alarms can mean that the instrument needs to be reset or that chemical vapors have been detected.

The worker supervisor in the tent also called the central shift office to report that workers had smelled a suspicious odor. At 8:10 a.m., the office declared a chemical-vapor incident, requiring workers to leave the area, according to tank-farm records.

An examination of the air-monitoring instrument showed the alarm sounded because of restricted air flow into the device, according to Washington River Protection Solutions.

The Department of Energy has said in court documents that workers may smell ammonia at low levels that are not a health risk. Real-time detection equipment available for ammonia is not as sensitive as the human nose.

In the Wednesday incident, 32 workers were in the area where the odor was reported, with nine of them reporting smelling odors and four of those reporting symptoms. No waste-disturbing work was being done in the area.

Because of medical privacy laws, details of symptoms are not released by Hanford officials. Typical symptoms are coughing, headaches, a metallic taste in the mouth and being lightheaded. Workers are concerned that chemical exposures could lead to serious respiratory or neurological illnesses.

Six of the nine workers reporting an odor requested medical evaluations at the Hanford on-site medical facility. All were cleared to return to work after an exam.

More than 60 Hanford workers have received medical exams for possible chemical-vapor exposure since spring.