Quantum of Solace Walkthrough

The red canisters on the ceiling are the haylon gas mentioned in the cell phone's text. They don't actually explode, but they will spray their contents all over and stun an enemy while he rubs at his eyes. Once you clear the area, look for the door at the back with the maintenance sign over it and head into the garage.

You will definitely want that weapons upgrade for the next encounter. Find the D.A.D system down this hall on the floor in the second room on the right. Then you can cover by those windows and start making guys go flying all over the place down there.

After the first wave, make like you're heading down to the floor. Take cover before you get there, though, and most likely you'll want to head back up (at least to the landing if not behind the windows again) once the guys start coming. The second wave runs straight at you, so it's hard to defend from the stairs. Since you're probably out of grenades to launch, you should grab a TND 16 Holo Sight off one of the bodies.