Factory Zero

Factory Zero is an achievement/trophy in The Missing Link DLC for Deus Ex: Human Revolution. It is earned by completing the DLC without upgrading augmentations and using weapons.

Overview
Factory Zero, like the Pacifist and Foxiest of the Hounds achievements in Deus Ex: Human Revolution, requires adhering to a specific playstyle from the start of the game until the ending credits.

As the achievement description says, you must fulfill these requirements throughout the whole DLC:

Requirements
 * Do not allocate any Praxis points, no matter how they were acquired: through level up or after collecting a Praxis kit.
 * Do not fire any weapons. Takedowns (lethal and non-lethal) are not considered weapons and can be used freely.
 * Do not throw grenades or place mines.

You can:
 * Throw red explosive barrels and fire extinguishers.
 * Pick up all items safely and sell them. However, it is not necessary to sell anything, because the starting credits (2500) are more than enough to buy all energy boosters and extra health items in the shop. Items that can be picked up include:
 * Praxis kits
 * Rocket launcher parts for the Quinn's Scavenger Hunt side-quest.
 * Quest items: Burke's eye, Data Storage Devices and the Trauma Kit.
 * Use healing and energy restoring items.
 * Equip, aim, upgrade and reload weapons. NOTE: This seems to be incorrect, at least on PC version 2.0.0.0.  To ensure you get the achievement, do not pick up any weapons at all, even your own.  You will have to do the mission twice if you want the achievement and your gear.
 * Equip explosives.
 * Trigger and/or disarm explosive wall mines
 * Trigger typhoon turrets (the rotating, beam-emitting turrets first seen on the third floor of the detention wing).
 * Get compromised and set off alarms, although that would make your mission considerably harder. You should try your best to keep a low profile and stay undetected throughout.

All of the Above

It is possible to obtain this achievement by using explosive barrels to destroy the large crate blocking the necessary vent, and then using several of the small boxes laying around to access the raised area in the ducts (2 should be enough). These can be carried (in the proper orientation) though the ducts, and dropped carefully to turn them on end. A well-thrown fire extinguisher can destroy the gas mechanism, but may require several attempts.

Bugs
The achievement may not be unlocked, even if all criteria are met.
 * One of the possible triggers for the bug is replaying the game with the "New game+" option. This issue also appears to extend to the pacifist and foxiest of the hounds achievements. It is recommended, if starting a new game, to not select this option.
 * Another possible trigger that may cause the bug is picking up, reloading, and/or modifying weapons. If attempting this achievement, it is highly recommended not to be equipped with any weapons but only consumables.