And, finally, a footnote for those of you who wondered about the wisdom of conducting sensitive sniff tests within breathing distance of a waste treatment plant.

When I asked NOAA’s Steven Wilson whether the, shall we say pungent, odor from the plant might not interfere with the experts’ razor sharp sense of smell, he said that wasn’t a concern.

“Believe it or not, our assessors can filter that out,” he said.

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

From the lab where the fish was dissected, we were ushered into a similar looking testing room, where three lidded Pyrex bows sat on the counter – one with red snapper, one with shrimp and one with oysters.

Steven Wilson, chief of quality control for the Seafood Inspection Program, demonstrated the techniques that a sensor would use.

But first he noted a deviation from NOAA's strict testing protocol: Seafood sensors usually work behind white cardboard partitions to ensure they don't pick up any visual cues from other sniffers. He also added another restriction that wasn't mentioned in this earlier post on testing procedures: Sensors don't wear rings while sniffing lest they pick up the slightest whiff of metal.

Then he pried the lid on the first bowl up about 2 inches, and used his other hand to waft a bit of air toward his nose, almost like a wine taster sampling a fine Cabernet Sauvignon. He then replaced the lid and stepped back.

He wasn't rocked back on his heels by the odor. Wilson explained that at this point in the process, the sensor is supposed to apply a single descriptor to the smell, maybe something like "smells like rubber bands."

Such a smell would likely earn the fishery where that sample was caught a "remain closed" rating from an expert assessor, but if 70 percent of the sensory panel decided it was OK, it would be cooked and then submitted to a second smell test, Wilson explained. Then, if it again was approved by 70 percent of the panel, they would taste it.

If 70 percent gave a thumbs up, the sample would be tested for 14 toxic chemicals at the Seattle lab, after which the fishery would be cleared for reopening if the results were negative.

One interesting footnote: Like wine tasters, seafood sniffers need to clear their senses between samples. The NOAA experts use watermelon and cucumbers to clear their nasal passages and eat saltine crackers between tastings.

Be back shortly with a bit more on the real hotdogs of the seafood sensory world.

Click here for the next post in the series: The 'top guns' of seafood sniffing

Sensory testing -- or sniffing -- is done under tightly controlled conditions. Tests are conducted in rooms with waterproof, seamless floors and smooth walls painted white, light gray or beige. The temperature must be between 68 degrees and 75 degrees with relative humidity at 45 percent. They can't be distracted by any other personnel, including fish industry officials – or reporters, said Steven Wilson, who oversees the inspections for NOAA.

The testers themselves must wash their hands with odorless soap and dry them with low-odor, white paper towels. They can't wear cologne or perfume -- although deodorant is OK, Wilson said -- and they must avoid eating spicy foods the day before and the day of the test, according to an industry manual.

A minimum of six 1-pound samples of seafood are collected. The testers smell each of the raw samples and record the odor, marking its intensity on a zero-to-4-point scale, with 4 being the most aromatic. They also note any unusual characteristics. An oil-tainted fish might smell "piney," for instance, with an aroma like Pine Sol cleaner, or it might smell "phenolic," with an aroma of Band-Aids.

The samples are then cooked and testers evaluate the cooked aroma and also take a tiny taste. They must spit out the samples, the manual says.

Now, let's see the process in action.

Click here for the next post in the series: A fine red snapper, with a hint of rubber bands

In case you were wondering, there are between 60 and 70 people in the U.S. trained as expert seafood sensory assessors.

They work for NOAA or the federal Food and Drug Administration and are usually charged with inspecting seafood shipments for signs of decomposition.

A person becomes an expert through a combination of natural ability, training and practice, said Steven Wilson, chief quality officer for NOAA's Seafood Inspection Program. The best testers can detect taint in concentrations as low as 1 part per million, he said.

"The issues that come up are just, literally, how sensitive their noses can be," he said. "Also, how repeatable their results are."

About 16 of those experts specialize in petroleum taint, said Wilson, with more experts being trained in this specialty every day. By the end of the summer, Wilson hopes to have at least 24 assessors "harmonized," a process that trains testers to detect oil and dispersants specific to the Deepwater Horizon spill.

Click here to read the next post in the series: Two filets: One for sniffing, one for the lab

By JoNel Aleccia, msnbc.com health reporter

While we're waiting for the sniffing to begin, let's address a question that several posters already have brought up:

Why use humans rather than chemical tests?

Using human assessors rather than chemical tests for first screening is a matter of efficiency and practicality, according to Steven Wilson, chief quality officer for NOAA's inspection program. Seafood that has a noticeably oily smell or taste is considered unfit for human consumption and can't be sold.

"If you actually smell oil in there, even though the chemical may be low and safe to eat, it won't be marketable," he said. "There are times when even it fails sensory, it passes chemical."

And suspect samples are chemically tested for PAHs – polycyclic aromatic hydrocarbons, the primary components of oil and tar. But that process is expensive and time-consuming. It can cost between $400 and $800 and take four days to test a batch of fish. Better to test only the fish that seem, well, fishy, Wilson said.

Click here to read the next post in the series: Deep sea fish on the sniffing menu

Msnbc.com was looking into seafood safety regulations and the protocols for reopening Gulf fishing areas when we came across a little-known but fascinating aspect of the seafood safety enforcement: the panel of secret testers.

NOAA officials already had noted they planned to use a panel of 10 expert assessors to decide when to open closed fisheries. But when we asked for the names of those experts, NOAA and the FDA balked at giving us a list, saying they feared for the accuracy and the safety of the testers if they were identified.

Then we learned that there's an entire industry of seafood sniffers -- and a place that trains them. The University of Florida operates a Professional Seafood Sensory School, which includes a targeted Shrimp School, that has trained some 500 students in the past 12 years, according to Victor Garrido, who helps coordinate the program.

Students usually come from government, industry or from private labs that are now being required to bulk up their testers' certification. Demand for sniffers could spike in the wake of the Gulf oil spill, Garrdio said.

We're live blogging about a NOAA briefing today in Pascagoula, Miss., where we'll get a chance to watch some 40 new sniffing recruits show off their talents.

Click here to read the next post in the series: Let the briefing begin ...

When oil from BP's Deepwater Horizon well finally stops gushing into the Gulf of Mexico, the decision about whether to reopen at least 81,000 square miles of waters to commercial fishing will rest with the trained noses and palates of a secret panel of nearly two dozen seafood sniffers.

They're the deciders, a group of experts -- highly skilled and exquisitely practiced in detecting unusual odors and tastes, including those of petroleum – that will largely determine the fate of the region's $659 million-a-year fishing industry.

Working for the National Oceanic and Atmospheric Administration, they will be charged with sniffing raw and cooked samples of 10 kinds of fish and shellfish, tasting a bit of each – and then deciding, yea or nay, whether an area can reopen.

"This is a major determination of the acceptability of the seafood coming out of the Gulf," said Steven Wilson, chief quality officer for NOAA's Seafood Inspection Program. "This is a major step."

Today you'll learn more about the program as msnbc.com live blogs a briefing at the NOAA lab in Pascagoula, Miss. Msnbc.com reporter Kari Huus will be on the scene, writing about a class of aspiring testers as they check a fresh load of seafood from the Gulf, and msnbc.com health reporter JoNel Aleccia will be filling in the facts and sharing interesting details about the testing program from our offices in Redmond, Wash.

When the oil-spewing Deepwater Horizon well is finally plugged or capped, which BP now hopes to accomplish by late this month, Wilson anticipates that he'll be running three "sensory crews" that will test up to 100 samples of seafood a day. For a specific geographical fishery to pass the first hurdle, five of seven testers on a panel must detect no trace of petroleum odor or flavor. If they detect any taint, that fishery remains closed. If the seafood passes, it is sent to a lab for chemical confirmation.

The new recruits are among some 40 state workers from the five Gulf Coast states that NOAA is teaching to be front-line testers. They will sniff fish on docks and in labs, determining whether the samples warrant further testing. If they clear the seafood, it will be sent to the secret experts, who are the final human arbiters.

That job is so politically charged that NOAA officials won't release the panelists' names. Officials say that the workers, including some who live in the Gulf Coast communities devastated by the spill, could face enormous pressure and even danger over their decisions about reopening the fishing areas.

"There are angry fishermen who are like, 'It's clean, let me in there,'" said Christine Patrick, a NOAA spokeswoman. "They're concerned not only for their objectivity, but for their safety."

The testers might have reason to be worried, said Capt. J.W. Berry, who runs fishing trips as a member of the Louisiana Charter Boat Association.

"If they don't open it back up, I can see them getting scrutinized," said Berry, 29, who also works as a New Orleans firefighter. "I can see them getting harassed and picked on. Not me, but I can see certain types of people doing it."

Click here to read the next post in this series: How we stumbled across the fish sniffers