A calibration technique for heat flow transducers (HFT) verified to within 5% by the National Bureau of Standards was used to show significant errors in calibration constants supplied by the manufacturer of the transducers. The effects of variable ambient temperature and hyperbaric helium on HFT signal responses were defined. Application of accurate calibration constants and appropriate temperature correction factors when using HFTs in hyperbaric helium allowed measurement of convective heat flow to within l0%.