The House voted 254 to 158 to impose a sweeping ban on use of lie detector tests by most private employers. The House acted after rejecting a substitute bill, 242 to 169, that would have allowed private polygraph tests to continue under strict new federal guidelines. Supporters of the ban, approved and sent to the Senate after more than 10 hours of intense debate, charged that polygraph tests were unreliable and constituted a threat to guarantees against job discrimination. House opponents of the bill argued that polygraph tests are a valuable weapon against employee thefts. The House approved exemptions for guards at sensitive installations and for drug company employees with access to controlled substances, among others.