The warning period ended 1 May 2022.

To be allowed to enter the Madrid municipality vehicles must meet a minimum standard of petrol Euro 3 and diesel Euro 4. Spanish vehicles have a sticker to show their emission standard. Foreign vehicles have to comply, but need no sticker. Spain doesn't issue stickers to vehicles that are registered abroad. 
Vehicles not complying are fined with 200€. 

For more information, see our Madrid page.

Picture source pixabay.