2005 Ford Focus air filter

No there is no button but make sure you got all the screws out and then just pry at it some times those housings can be stubborn and don't want to come off easily

On the contrary, be careful as to which air filter system you have. There are two:

One filter type is mounted near the firewall, above the brake booster. This is a disposable-paper type with four screws, usually a combo of flat blade or 8mm hex.

The other filter type is near the radiator, further down in the engine compartment. This is a factory permanent foam type. Not servicable. It is expected to last the life of the car. Don't try to pry this one open.

The two types are easily distinguished. Just follow the air intake snorkel hose. It'll either go to the firewall, or stay near the front of the car towards the radiator.