Some 70 area companies are preparing to showcase their products and services Tuesday at the Greater Hall Chamber of Commerce’s Buy Local/Safe & Green Expo. The event will provide “networking opportunities” for businesses and others attending the free event, “but it’s also about local businesses getting a chance to show people what they do,” said Megan Martin, the chamber’s vice president of membership development. The expo used to be two separate events — one focusing on businesses and what they do, and the other on companies’ environmentally friendly practices.