I have forced hot-air Oil Head but the vents look like Baseboard heater vents

[Anonymous]

I am not sure but this sounds like a Linear and Slot diffuser. I have never seen these used in a residential dwelling. They are made for Commercial use. There should be screws that hold the cover to the frame. Clean with a vacumn cleaner and soap and water.  Here is product manual on the ones I am refering to, pages 6 & 7:  

Hope this helps.

[Stef]

What are these type of registers called? Who - what can clean this style vent?