Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification
Aircraft
Cruising at FL250 we heard a pop and my ears plugged. Captain immediately went for the oxygen masks and then I followed. Established communication and executed an emergency decent to our assigned altitude of 9;000 feet. Captain was the PM (Pilot Monitoring); [and requested priority handling] and got out the QRH. Structural damage was not suspected so we descended at 300+kts with full speed brakes. I was monitoring the cabin altitude pressure and it did not go above 14;000 feet until well established in our descent. When it finally did; we got a level 3 warning message and shortly after flight attendants called up. I made an announcement to the passengers to put on their oxygen masks. Captain also tried to call Dispatch with no answer. [The Captain] followed all procedures and communicated with all involved. Minutes went by [before] I could take time to think and observe. It was loud in the cockpit. It sounded like the leak was somewhere in the cockpit but I couldn't find an air source. It was very loud; hard to hear [the Captain] talking. We made the decision to continue to [destination] because at the time we were 44 miles away and 43 miles from [a possible alternate]. [The Captain] made announcements to the passengers probably 2 times and talked to the flight attendants whenever they called (3 times at least). On one call; flight attendants said they smelled a burning smell; and then we could smell it too (likely the chemically [generated] oxygen which I realized after the flight). We elected to keep our speed at 300+ knots to get to [destination] as soon as we could just in case there was a fire somewhere on board. We ran all appropriate check lists and Captain had me continue to fly the plane to landing. We stopped on the runway and met by fire trucks. They did a walk around deemed it safe and we taxied to the gate on our own power.
B717 First Officer reported loss of cabin pressure at FL250.