The dress code nobody actually sends you

No invitation states a dress code plainly, and the phrase that comes closest — “business casual” — carries a different weight depending on which room you’re standing in. A federal advisory committee reads it as a blazer and closed-toe shoes, no tie strictly required but nothing that would look out of place at a deposition. An exhibit hall reads the same two words as a polo, comfortable footwear, and a badge that stays visible for six hours of walking. Neither organizer is being vague on purpose; the phrase was never precise enough to carry the weight put on it, and guessing wrong in either direction costs something — overdressed reads as trying too hard on a trade-show floor, underdressed reads as not taking the room seriously in front of a regulator. The fix isn’t a stricter rule from the organizer. It’s reading the room’s own function before you pack, the same way you’d check a listing’s format before you register for it.

No one states it, so you read the room instead

An organizer can’t specify a dress code precisely because it doesn’t control who walks in wearing what, and “business casual” is the safest phrase precisely because it commits to nothing. The honest signal isn’t the registration page’s wording; it’s the room’s own function. A session where someone is building a formal transcript, taking attendance for a public docket, or presiding as a government official reads differently than a session built for browsing and small talk. Before packing, it’s worth sorting each day of the agenda into one of those two buckets rather than treating the whole trip as a single dress-code question.

Government-facing rooms run more formal than you’d guess

A room where a federal advisory committee is meeting, or where a public meeting is building an official record, tends to run more formal than a professional-society track session even when nothing on the agenda says so — a listing like an FDA advisory committee day is a useful gut check for the register. The same holds for a hearing room or a venue that runs real security screening: those are rooms built around a proceeding, not a reception, and a suit is rarely the wrong call in either. If the organizer’s own site or past-agenda page shows photos from a prior year, that’s worth a look before assuming; checking at the source works as well for a dress norm as it does for a start time.

The expo floor is where the rules relax

A trade-show hall spanning several exhibit halls is a different physical job — walking for hours, standing at booths, carrying a bag — and the dress code follows the job rather than the industry’s reputation for formality. Footwear matters more than the jacket on a floor like that; a blister by mid-afternoon does more damage to the day than a slightly casual shirt ever would. It’s also the setting where overdressing reads oddest: a full suit worn to walk an exhibit hall for six straight hours looks like someone who hasn’t done this before, not someone taking it seriously.

When in doubt, layer and check the photos

The practical answer for a week that mixes both kinds of room is a small wardrobe that layers rather than a single outfit chosen to split the difference: a jacket that comes on for the formal sessions and off for the floor, shoes that survive a full day of walking without looking wrong in a hearing room. If a colleague attended the same event last year, a two-line message asking what the room actually looked like beats guessing from the program alone — and it’s the same instinct worth building before any first conference, where the logistics nobody puts on the agenda tend to matter more than the sessions themselves.