When Nancy Fraley was here on business earlier this month, she had to ask the staff at the Grand Hyatt downtown for a room change. And another one. And again.

“The aromatics were annoying,” she explains. Even in the room she finally settled on, she says she kept on asking them if there’d ever been a fire in there. “I can tell that,” she says.

Fraley admits that going through life with an overactive sense of smell can be “a liability.” Except when she’s working. In fact, as one of the country’s few traveling master whiskey blenders, Fraley’s nose helps her earn a living.

One of her two dozen–odd clients is Jos. A. Magnus & Co., the micro-distillery above Atlas Brew Works in Ivy City. The Berkeley, California, resident was in town on one of her regular visits to check on the distillery’s stock of whiskey barrels and to begin pondering how each barrel will be used—maybe one will end up in Magnus’ Cigar Blend whiskey, another might play a part in the next iteration of the recently released Family Reserve that runs $1,000 per bottle.

One note on Jos. A. Magnus & Co. barrels: The liquor in them wasn’t distilled on premises, as house-made whiskies must age for years before they can be bottled and sold (Magnus opened in August 2015). So like many young distilleries, to get bourbon to market they “source” whiskies from another producer, then blend and bottle them in their own facility. (Some are more honest about it than others.) Most of Magnus’ sourced barrels were made at MGP Ingredients, a massive operation in Lawrenceburg, Indiana, and aged at Heaven Hill in Kentucky.

That’s where Fraley comes in. Her role is to snuff out specific barrels in the warehouse that have the characteristics Magnus is after. From there, it’s deciding how to blend those various whiskeys—and, perhaps, finish them in yet another barrel in D.C.—to reach the final product that will be bottled.

Magnus is unique in that there’s a reference point for that ultimate goal. It was a big brand before Prohibition, and after its 2015 resurrection, the current owners sought to replicate its original whiskeys as much as possible.

To get from point A to point B, Fraley sniffs and tastes constantly. But mostly sniffs. She says her nose accounts for about 90 percent of it, and watching her work is proof. “I get a lot of nutmeg notes, some allspice, and baking spices,” she says, upon sticking her nose in a tasting glass. “Have you ever had an English Christmas cake?” she asks after tasting another. “I also get an aroma that’s called pruneaux … stewed prunes in Armagnac sauce.”

Her vocation in undoubtedly more art than science, but she has a nuanced left-brained way of explaining it. “I always think about it like a pyramid,” she says. “You have different tiers. You start with the legs, the base components. The base whiskeys have a lot of wood sugars, caramel, toffee, vanilla. But the next layer you want to start filling in the gaps. Maybe I’m not getting enough mouthfeel or fatty acids, or spice or citrus. Whatever it is, I’m filling in until I get to the top.”

Other times, Fraley’s services are more immediate. For start-up distillers, her elevated olfactory sense can sniff out any problems along the way as the new operation finds its legs. Some make mistakes in the fermentation process. Others aren’t sure where to make the “cuts” as the new hooch comes off the still, which can leave too much acetone or undesirable oils in the spirit.

A brown spirit, she says, is “conceived with simple sugars from a raw ingredient and yeast, and then it spends time in a copper womb. Then it’s “born” from the still. She views her role as “raising the barrels from being toddlers through adolescence to full maturity.” That may involve moving barrels around the warehouse from cooler, lower spots to higher, warmer locations or slowly adding water to a barrel to gradually bring down the proof before bottling.

“I couldn’t put a time limit on how long it takes,” she says. “It’s just ready when it’s ready.”