Summertime is prime time for CO2 regulator freeze up. This condition is more than just frost or condensation on the outside of the regulator. When CO2 flows through a regulator from a cylinder heated by the sun or high air temperatures (and therefore at an increased pressure) and is reduced to a much lower working pressure, the difference in the high pressure inlet and the low pressure outlet causes a drop in temperature which can be great enough to cause the CO2 gas to freeze and form dry ice. This can be in the form of "snowflakes" that accumulate on the internal components of the regulator and eventually cause complete blockage and loss of flow.
Heated regulators can relieve or eliminate freeze-up problems. The Harris Model HP 705 has 200 watts of heat to provide a continuous 100 scfh of CO2 under the most severe freeze-up conditions and higher flowrates under normal (intermittent) conditions.
The regulators are two-stage: the first stage cavity serves as a boiler to vaporize CO2 liquid and eliminate or minimize any CO2 solids in the second stage. The second stage chamber is then available to heat the CO2 vapor before it reaches the outlet.