Know the Difference Between HTHV and 80/20 Technologies - It Makes a Difference To Your IAQ!
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 introduces 100% outside air without recirculating building air through the heater, which can provide important IAQ benefits when properly applied. 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
Frequently Asked Questions
What is HTHV?
High Temperature Heating and Ventilation (HTHV) is a direct-fired, 100% outside air technology used to heat new construction and retrofit projects.
What is an 80/20 unit?
An 80/20 unit is a recirculating direct-fired heater. Like HTHV, it has been used for heating in new construction and retrofit projects across the US.
What is the main difference between the two for indoor air quality?
The difference is the amount of pollutants, measured in parts per million (PPM). HTHV is the clear winner on IAQ. The infographic above compares the PPM levels of each technology against the acceptable limits in the US and Canada.
What does OSHA consider good IAQ?
OSHA says good IAQ includes comfortable temperature and humidity, an adequate supply of fresh outdoor air, and control of pollutants from inside and outside the building.
Who sets the acceptable pollutant limits for workplaces?
Both OSHA and the Canadian Standards Association (CSA) set limits on acceptable PPM levels for different pollutants in working environments.
Which performance and safety standards apply to each technology?
ANSI Z83.4 covers 100% outside air, non-recirculating, direct gas-fired industrial air heaters such as HTHV. ANSI Z83.18 covers recirculating direct gas-fired industrial air heaters, which are the 80/20 units.