Saturated fluorocarbons (SFCs) of form C n F (2 n +2) are chosen for their optical properties as Cherenkov radiators, with C 4 F 10 and CF 4 currently used at CERN in the COMPASS and LHCb ring imaging Cherenkov detectors. Their non-conductivity, non-flammability and radiation-resistance also make SFCs ideal coolants: C 6 F 14 liquid cooling is used in all LHC experiments, while C 3 F 8 is used for the evaporative cooling of TOTEM and the ATLAS silicon tracker. These fluids, however, have high global warming potentials (5000–10000*GWP CO2 ), and represented around 36% of CERN’s CO 2 -equivalent emissions in 2018. There is thus an impetus to reduce their use, losses in purification and wastage through leaks, through improved monitoring and closed circulation system design. Newer spur-oxygenated fluoro-ketones, for example from the 3 M NOVEC ® range, with C n F 2 n O structures, can offer similar performance to SFCs with but with very low, or zero GWP. Although these fluids do not yet exist in large quantities over the full C n F 2 “matrix” the radiation tolerance and thermal performance of NOVEC 649 (C 6 F 12 O) was sufficiently promising for it to be chosen as a C 6 F 14 replacement for cooling silicon photomultipliers. Additionally, subject to optical testing, NOVEC 5110 (C 5 F 10 O) could (if blended with nitrogen) replace both C 4 F 10 and CF 4 in Cherenkov detectors. Lighter molecules (for example C 2 F 4 O, with similar thermodynamics to C 2 F 6 )—if and when available in industrial quantities—might allow lower temperature operation than evaporative CO 2 in future silicon trackers operated at very high luminosity. Ultrasonic gas mixture analysis is very sensitive to concentration changes of a heavy vapour in a light carrier, and is used—in the only such fluorocarbon coolant leak monitoring system operating at LHC—for real-time monitoring of C 3 F 8 coolant leaks from the ATLAS pixel and SCT silicon trackers into their nitrogen-flushed environmental volumes. A typical C 3 F 8 sensitivity of better than 10 −5 is achieved. Advanced new ultrasonic algorithms allow measurement of the concentrations of a pair of gases of particular interest on top of a varying known baseline of other gases. The technique is thus of considerable value in leak monitoring and could be used to blend fluoro-ketones with nitrogen or argon to reduce the GWP “load” of large volume atmospheric pressure gas Cherenkov radiators without the recourse to higher-pressure noble gas approaches. This paper outlines an approach to GWP reduction with fluoro-ketone fluids and the blending of heritage SFCs or fluoro-ketones with lighter gases using ultrasonic monitoring and control. Possible avenues for the use of fluoro-ketones in liquid phase and evaporative cooling of silicon trackers are discussed.