### Question
How is the "heat input" defined?


### Answer
The term **heat input** is defined in *40 CFR § 52.01* as follows -

> the total gross calorific value (where gross calorific value is measured by ASTM Method D2015-66, D240-64, or D1826-64) of all fuels burned.

#### Citation:
  - *40 CFR § 52.01*
  - Heading: **PART 52—APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS > Subpart A—General Provisions > SUBCHAPTER C—AIR PROGRAMS (CONTINUED) > SUBCHAPTER C—AIR PROGRAMS (CONTINUED)**

