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:
What is considered good IAQ?
The qualities of good IAQ should include comfortable temperature and humidity, adequate supply of fresh outdoor air, and control of pollutants from inside and outside of the building2
It is these pollutants, and the amount of the pollutants in parts per million (PPM), that differentiate 100% outside air HTHV technologies apart from 80/20 units. Both OSHA and the Canadian Standards Association (CSA) set limits on what the acceptable PPMs for different pollutants are for working environments. The performance and safety standards set by the American National Standards Institute (ANSI) are z83.4 for 100% outside air non-recirculating direct gas-fired industrial air heaters and z83.18 for 80/20 recirculating direct gas-fired industrial air heaters. The infographic below helps illustrate the differing amount of pollutants in PPM between HTHV and 80/20 units along with the acceptable limits for these pollutants in both the US and Canada.
1 Reference OSHA website: www.osha.gov/about.html
2 Reference OSHA website: www.osha.gov/OSHA_FAQs.html