Heat Production and Temperature in the NINA Heater Ten replicate runs of the optimized prototype displayed minimal variation in temperature from run to run within the reaction tubes ( Figure 1 ). The heater reached the optimal incubation temperature in 15 minutes, and maintained the target temperature with minimal drift over 60 minutes. (Drift from minimum to maximum temperature within run, mean over all runs = 2uC.) Comparison of the temperature plots for the CaO, EPCM, and reaction tubes in Figure 1 to Figure 1B in Hatano et al. [27] illustrates the beneficial effect of having the EPCM component in the heater. The CaO temperature traces show rapid and poorly controlled heat generation, with maximum temperatures exceeding 100uC. The traces of the EPCM at the interface with the CaO have a pattern similar to the CaO, but the initial temperature excursions are reduced in magnitude, and the plots are far more repeatable. Finally, the reaction tubes display only a uniform ramping to the target temperature followed by a prolonged stable isothermal phase. The temperature in the NINA reaction appears more uniform than that shown by Hatano et al. [27] for their hand-warmer device.