RO system drains into a sewer line. Is a trap and air gap required?

Reverse osmosis drinking water filtration system drains into a waste line in the basement. On one side the line terminates at the bar sink than the RO system drains into the horizontal line which drains into the 4 inch vertical sewer line. Shouldn’t this drain into a trap? Is an air gap required?
Thank you for your help!
Have a blessed day!

Amy Miller 120.JPG

Very common, should be installed before the ptrap under the sink.

Best practice, IMO… http://www.freshwatersystems.com/p-26-dla-9-drain-adapter.aspx?utm_source=pricegrabber&utm_medium=Feed&utm_campaign=Product&utm_term=DLA-9

Thank you all I appreciate the help.