pyro-, pyr- +

(Greek: fire, burn, burning, heat, produced by heating, hot; and sometimes also referring to "fever as shown at this link")

pyrotic
1. A caustic, or burning, medicine.
2. A reference to "heartburn" or pyrosis.
pyrotoxin
Any toxic agent produced by combustion or a fire.
pyroxanthine
A yellow, crystalline substance obtained from creosote, etc.
pyroxylophilous, pyroxylophile, pyroxylophily
Thriving on, or having a fondness, for burned wood.
solarimeter, pyranometer
1. General name for the class of actinometers that measure the combined intensity of incoming direct solar radiation and diffuse sky radiation.
2. An instrument used to measure the combined intensity of incident direct solar radiation and diffuse sky radiation.

It operates by comparing the heat produced by the radiation on blackened metal strips with that produced by a known electric current.

Cross references of word groups that are related, directly, indirectly, or partly to: "fire, burn, glow, or ashes": ars-, ard-; -bust; cand-, cend-; caust-, caut-; crema-; ciner-; ether-; flagr-; flam-; focus, foci-; fulg-; gehenna-; ign-; phleg-; phlog-; pyreto-, -pyrexia; spodo- (ashes; waste); volcan-.