By JoNel Aleccia and Kari Huus, msnbc.com

A final word about the "top guns" of seafood sniffing.

Known as expert assessors, there are only 18 of them on NOAA's payroll. These are the experts who are capable of smelling 1 part per million of contaminants, according to Steven Wilson, the chief quality officer of NOAA's Seafood Inspection Service.

To prepare them for their duty in the Gulf, NOAA sent them to Gloucester, Mass., for "harmonizing" – a process in which they repeatedly sniffed samples from the BP oil smell until they could agree on common descriptors for the odor of the oil from the Deepwater Horizon.

As noted in this previous post, Wilson is hoping to build the expert squad up to 24 to help handle the crush of work in the coming months.

In addition, NOAA recently held three three-day sessions for state screeners. These were people who already were working as fish inspectors or lab personnel and had some training in the sensory arts. With the refresher training, Wilson said, they will be able to detect 10 parts per million of contaminants and help prevent the expert sniffers from being overwhelmed.

That will leave the agency's finest-tuned noses to concentrate on the most delicate decisions that lie ahead: When areas will be reopened for fishing.

That's why, though Wilson was willing to appear on camera, he steadfastly refused to identify the expert assessors and said he would strongly resist any efforts to force disclosure.

"We're in the middle of an industry under stress," he said, referring to the hard-hit Gulf commercial fishing industry. "These assessors stay here for two weeks at a time. We don't want any kind of pressure on them to make some kind of determination."

He said many of the assessors have expressed concerns about possible repercussions, adding, "I would push hard to support their fears and their concerns in this issue."

Click here for the final post in the series: Tuning out is just as important as sniffing