Still Spirits Heat Turbo Yeast (previously Heat Wave Turbo) is the only Turbo to use when the air temperature is above 33C. Delivers excellent quality alcohol in hot conditions. Heat Wave is also the only yeast we recommend for `stacking `. Up to a 200 litre volume can be fermented using 8 sachets (providing the start liquid temperature and air temperature are both 20C). Turbo Carbon is recommended as well, as it will significantly improve the performance of Heat Wave Turbo.