A question hung in the air at the Cannabis World Congress and Business Exposition at the Jacob K. Javits Convention Center in Manhattan on Thursday: How do you show off your wares in a place where actually using them would be illegal?

The sales pitches were carefully honed.

“These are for tobacco only,” Raj Tiwary, a vice president for the vaping accessory maker Ultimate Vapor Source, said repeatedly, while demonstrating a line of pipes and pens. “Tobacco and dry herbs.”

Nearby, a set of self-watering pots housed several thriving tomato plants — “the pots work well for all kinds of plants,” Marc Lippman, the co-owner of Aqua Camel, emphasized — and a $2,000 vacuum sealing machine showed off its power by endlessly reinflating and resealing a pouch stuffed with spinach. One row over, Vaughn Fitzgerald, a representative of Desiccare, illustrated his company’s packaging system for preserving organic matter.

“You put your weed in here — in theory — and seal it up, and it’ll stay pristine for the next 15 years.” Asked about the sample “weed,” which looked like florists’ moss, Mr. Fitzgerald laughed and replied, “It’s New York, hon. We all gotta play the game a little bit.”