Keep the response protective
Do not chisel inside the pipe, apply flame or hot water, add improvised heat tape, remove a termination fitting, or keep restarting the furnace. Do not disconnect the intake so the furnace draws air from another location. Those changes can alter the installed vent and combustion-air arrangement.
For example, Trane's owner manual says a blocked vent can trigger furnace shutdown and calls for qualified service. A protective shutdown is a reason to find the cause, not bypass it. Trane blocked-vent instruction.
Document the exterior condition safely
From a safe ground-level position, photograph where ice appears and note the weather, snow accumulation, and time until blockage returned. Do not climb onto an icy roof or use a ladder to reach a termination. Share existing furnace model information and any accessible fault message.
Lennox recommends checking exterior intake and exhaust for winter obstruction and getting professional help when they are not easily accessible. Lennox winter intake guidance.
Ask for the full installed arrangement to be checked
Ask the technician whether the intake and exhaust locations, termination configuration, pipe routing, and drainage follow your exact model's instructions and the applicable installation requirements. Ask what evidence explains repeated icing and whether the proposed work addresses that cause. Do not accept a generic screen, cap, or relocation suggestion without checking its approval for the equipment.
If the work needs another provider or building change, have responsibilities and quote inclusions stated. Ask how the corrected installation will be checked and what observation is needed when similar weather returns.
Make waiting realistic
Tell the provider the indoor temperature and who needs heat. If safe temporary heat cannot maintain suitable conditions, arrange a warm place to stay. A room heater does not prove the rest of the house is protected.
Use portable electric heaters only as their instructions allow. Keep three feet from combustibles, plug directly into a wall outlet, and turn them off when leaving the room or sleeping. EPA temporary-heater guidance.
Your next step is an urgent service request for recurring intake blockage, with the photos and waiting needs included. Keep the furnace out of use until the qualified assessment establishes the operating recommendation.