Indoor wall covering

I inspected a home that had a finished basement which included a large storage area which contains the electrical panels, water heater and heat pump air handler. The wall, on the inside of the storage area, had a material that looked like 1/8" cardboard on it. It has no markings about being flame resistant. This is the first time I have run into this. My instinct is to call it out as a defect but I am not sure. Let me know what you think.

Do You have any pictures ?

Not yet, doing the inspection tomorrow.