TOPIC: What is this in plenum?

1986 Calif Condo, it appears to be an electronic filter but I'm not familiar with it. If it is an elec filter, do you have to unbolt/unscrew it to service it?

Hi,
Your photo is taken from a bit odd angle, actually from the top of the unit. The service panel would probably be more in the front of your picture. Yes, this is an EAC (electronic air cleaner), and to service it, normally does not require any "unbolt/unscrew action. The cell, what you see on the photo, could be called "cell nr.2" ! The reason for that is because there is a place for "cell nr. 1", in the front of a picture. Normally, when both are in place, there is a service panel in front of them, so you , if there is a need to access it, would have just to open a panel, and slide out first "cell no.1", and then "cell no 2" . no screws or bolts removed. If they require cleaning , then dish washer is a good place to do so. But, with so much of a dust inside plenum and ducts, I feel free to say that's not gonna help a lot! Those ducts are in need of a good duct cleaning action first.
Regards, Joe HH