Black plugs on HVAC ducts?

[Mike Lamb]

I often see these black plugs on HVAC ducts. What are they for?

[Marc]

Inspection or sampling ports?

[Jerry Simon]

For duct cleaning.

 

[Bill Kibbel]

It's where they inserted the "pneumatic agitation tools".

[Mike Lamb]

Thanks. I should have Googled first. I thought cleaning from the registers would be easier.

[Bill Kibbel]

2 hours ago, Mike Lamb said:

Thanks. I should have Googled first. I thought cleaning from the registers would be easier.

They do.  The holes are for inserting the tools that agitate the dirt.