How do I know my windows are gas filled ?
Tilt ins. Older but in great shape. Rubber flaps in between is unreachable and shows spotted mold. There are 2 screws on top of each window piece looking like u could open to remove mullions. But don’t know if they are gas filled and if would ruin 38 tops and 38 bottoms! No fogging -want to clean that unsightly mold off rubber edging inside!