For years High Temperature Heating and Ventilation (HTHV), a direct-fired 100% outside air technology, and 80/20 direct-fired units have been heating solutions used for new construction and retrofit projects throughout the US with little attention to the differences in Indoor Air Quality (IAQ) from both products. However, when it comes to IAQ there are significant differences between these two technologies – HTHV being the clear winner. The Occupational Safety and Health Administration (OSHA) was created to assure safe and healthful working conditions for working men and women by setting and enforcing standards and by providing training, outreach, education and assistance1. Among the frequently asked questions on the OSHA website is one concerning IAQ: