Many trade shows are held in the Washington, D.C. area. Jewelry, cars, electronics and other industries have shown their products and services in the past.

　　But recently Washington was home to a trade show representing a new industry – new, that is, to the legal sales world. The ComfyTree Cannabis Academy held a marijuana trade show just two days after the city legalized use of the drug.

　　Industry representatives demonstrated smoking equipment and marijuana plant growing systems. Some even gave business advice about what supporters hope will be a successful industry.

　　It is still a violation of federal law to possess marijuana. And Washington D.C. law still does not permit sales of the drug. For these reasons, the trade show did not feature marijuana itself. But there were new, small businesses with products designed to grow the plant or use it.

　　All tickets for the two-day event were sold out. Keith Carey was among the attendees.

　　"I love marijuana so it's best to find out what everyone is starting to do for it."

　　People in their 20s came to the show. The oldest attendees were in their 70s.

　　Many came just because they were curious, like David Jackson.

　　"I was just interested in what comes with this new legislation that passed...to take advantage of the new freedom we have."

　　Manufacturers demonstrated things like lighting systems and planters. Eric de Feo showed his seedling planter, called ROOT. He said it was designed to grow vegetables inside a house or other structure.

　　"We really didn't start getting traction with this product until it was suggested you can use this for cannabis."

　　In Washington, it is now legal to grow up to six marijuana plants at home. David DeGraff is the owner of The Grow School in Colorado. He told the show's visitors about his online classes to teach marijuana growing.

　　"How to set up their grow room properly, how to water and fertilize, how to solve problems."

　　Users who want to know more about the many kinds of marijuana can turn to free computer application software from the on-line service Leafly. Its co-founder, Cy Scott, said the most popular kind of plant is called Blue Dream.

　　"It's a pretty readily available strain and it's also one that doesn't put you to sleep like so many do, so people really like it."

　　But how can you know if your marijuana is safe to use? Businessman Terron Gray has a machine that can tell you. For a payment, he will test marijuana for its potency and dangerous chemicals, like pesticides. And he will bring the machine to you.

　　"And I'll take my machine to whatever residence or wherever you want to be to test your cannabis."

　　Chris Wrights owns Scentless, a business based in Maryland. He sells air purifiers for marijuana.

　　"We've designed filters for the indoor gardens and tents that will remove 100 percent of the odors so you can grow it discreetly."

　　Visitor Katie Eye says she is considering a career change after seeing all the products at the show.

　　"There are plenty of businesses it seems here of interest, a lot of marketing opportunities, sales for the future."

　　I'm Caty Weaver.

　　VOA's Deborah Block reported this story. Caty Weaver wrote it for Learning English. George Grow was the editor.