Gas heaters for Snow Shield Cover De-Icing Systems and new CE Certified Gas Heating Unit’s Features: New Dual Hot Surface Ignition System Dual hot surface igniter’s means redundancy in the ignition sequence. Large flame sensing rod. Turbulence no longer a factor during ignition sequence. Same reliable 3 try ignition sequence with purge time. No more pilot assembly or pilot orifice. Positive Blower Recognition for Ignition Sequence. Normally open contact on air flow switch operates power to the ignition unit. No air flow, no ignition. If no airflow is verified, the ignition unit will not be energized and the unit will go into ignition failure mode.