Lt Christine Malone has volunteered to walk through the plant and draw out some dangerous criminals. She's counting in you to keep her covered. Don't let her down.
This match is hell on hot toast. Although the Chemical Plant escort is among the shortest, you're dealing with so many enemies at once, it's very easy for Malone to die to an inattentive player.
Always keep the catwalks above in sight - Enemies can and will shoot at Malone from them.
Keep your eyes glued to any possible attack routes. If Malone starts taking damage, immediately rush towards the aggressor and gun them down.
Uzi x2 is your best friend for the most part. Ammo is plentiful, and it kills enemies in a good click. Save the M16s for near the end, because ammo for that is far harder to get.
If you die, there's no chance to recover. The enemies will kill her before you arrive. So don't get shot in the head!