These achievements aren't related to any chapter in particular.


Caffeine Extraction
Perform surgical caffeine extraction from 20 machines.


For this achievement you need to extract 20 cans from vending machines, you'll find them all throughout the game so you shouldn't have any trouble, just keep interacting with one of the machines until the buttons go red and you can no longer get any cans. It might take a couple vending machines before the achievement pops!


Prophylactic Suggested
Get overtaken by a Headcrab's ample anterior.


Die from a Headcrab to unlock this achievement.


Well-Done
Cook a grenade for too long.


Pull the pin and don't let go long enough for it to explode in Gordon's hand.


Calculated Trajectory
Kill 10 Airborne Headcrabs using the Shotgun.


Self explanatory achievement, whenever a Headcrab jumps towards you just shoot it mid air.

Rare Specimen
Send the Hidden Hat to Xen.


You can find the Hidden Hat during Chapter 3: Unforseen Consequences, a little bit into the chapter you'll return to the front desk area from the start of the game, instead of going through the vent to your right, go back out towards where you got off the train on your right are some pipes you can jump on, the hat is hidden in the corner. Once you have the hat you'll need to painstakingly carry it from here to the end of Chapter 14: Lambda Core, and place it in the teleporter.

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The Rarest Specimen
Carry the Hidden Hat to Endgame.
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Same as the achievement above, however once you've sent the hat through the teleporter to Xen you'll need to continue carrying it to the Nihilanth fight.


Pepperoni Precipitation
View the *other* secret ending.


Similar to the Hidden Hat achievements, instead you'll find the pizza box during Chapter 11: Questionable Ethics. Carry it all the way to the Nihilanth fight for the achievement. You can find it on the bench in the cafeteria.

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Once you reach Xen you'll need to find the hidden hat and the pizza box again. You can find them a bit into the chapter, after doing the jumping puzzles, you'll reach the orange crystals that lower your Suit Power/HP, just after these crystals there's a cave across from you with a dead scientist in it, this is where you can find the hidden hat and pizza box, double jump across to the cave, in the back corner in a little hole you'll find the hat and/or pizza.
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Proverbial Tinkerer
Interfere with the alarm and laptop in Anomalous Materials.


After the introductory train ride you'll reach the front desk of the research facility, on your left as soon as you walk in is a computer you can interact with, after that walk behind the desk and press the button to the left of the scientist. You can't press the button immediately, you have to wait until the security guard has finished speaking. Video below if you're lost:



Convection Refinement
Ruin the microwave casserole.


From the front desk follow the green line on the wall, eventually you'll reach the break room. Inside the break room interact with the microwave and after a few seconds you'll ruin the casserole and unlock this achievement.




Brownian Motion
Pass the toilet paper to the scientist in need.


If you continue following the green line you'll reach the locker room where you'll find the HEV suit. On the other side of the room is the bathrooms where a scientist in a stall will ask for some toilet paper, pick it up and hand it to him underneath the door for the achievement.

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Less Than Desirable Consequences
Die in the AMS Beam before starting the experiment.


Near the start of the experiment a large laser will appear in the middle of the room, for this achievement all you need to do is walk into it.




Resonance Procrastinator
Refuse to insert the specimen into the Anti-Mass Spectrometer.


Not long after the achievement above a delivery cart will appear that you need to push into the laser, for this achievement do NOT touch the cart. After around a minute you'll unlock the achievement.

Inflammatory Actions
Kill a Headcrab using fire.


This achievement is easily done during Chapter 3: Unforeseen Consequences. Touch a Headcrab with one of the flares to kill it with fire. Be careful if you have a security guard following you as he may kill it before the fire does. You can easily unlock this achievement once you reach the front desk area again, pick up one of the flares on the desk then run out to the gates towards where you got off the train ride earlier, on your left in a small room is a Headcrab.



Mega Hertz
Kill 5 enemies with one grenade.


There's a good location to unlock this achievement during Chapter 3: Unforeseen Consequences. There's a group of 6 Barnacles in a hallway, make sure you use the barrels to get past them without killing them, ask the scientist to come with you so he'll unlock the security room, that way you'll have access to the grenades. Now backtrack and throw a grenade at the right-most Barnacle for the achievement.

Our Brains And Your Brawn
Assemble all the possible Scientists and Guards at the end of Office Complex.


For this achievement you'll need to successfully escort every possible guard and scientist to the elevator at the end of the level. (4 guards and 2 scientists)



Permeable Infrastructure
Use the alternate path in Office Complex.


You will get this achievement if you follow the achievement above as you'll need to take the alternate path to turn off the sentry turret.

Digital Wizardry
Kill 10 enemies with a reprogrammed Sentry.


Starting from Chapter 5: We've Got Hostiles if you stand behind a Sentry Gun and pick it up you will 'reprogram' it and it will begin to shoot enemies instead. Run around with the sentry gun aiming it at enemies for the achievement.


Kinetic Repulsion
Kill a Marine with their own grenade.


You can farm this achievement quite easily when you meet the first marine of the game, instead of killing him just hide behind a corner and wait for him to throw a grenade, pick it up with E and left click to throw it back at him. If you don't succeed you can just wait and he'll keep throwing them.



Unified Coupling Theorum
Help the Barnacle and Headcrab find true love


There is a good location during this chapter where you can easily farm this achievement. It requires you let 10 Headcrabs be caught and eaten by a Barnacle. There is a Barnacle right at the end of the first conveyor belt you come across, run down the conveyor belt and you'll find a room full of Headcrabs, bait one of them onto the conveyor and wait on the other side of the Barnacle, quicksave your game just before the Barnacle grabs it. Once it's eaten the Headcrab reload your quicksave, repeat this 10 times and you'll unlock this achievement.

Remote Detonation
Kill a Barnacle with a Satchel.


During Chapter 6: Blast Pit you'll unlock Satchels, for the achievement just throw a Satchel at a Barnacle's tongue and detonate it once it's close enough to the barnacle itself.


Gray Matter Propulsion
Headshot 20 enemies with the .357 Magnum


You first find the Magnum during this chapter, self explanatory achievement just get 20 headshots with it.
*Apparently Assassins don't count towards the total.

One Step Ahead
Kill 10 Enemies with Tripmines.


You'll unlock Tripmines in Chapter 7: Power Up, simply get 10 kills with them for the achievement.
You can farm this achievement easily by putting a tripwire down, save, then lure an enemy into it, reload and repeat until you have the achievement.

Dead Reckoning
Kill an Assassin with the .357 Magnum.


Assassins will first appear during Chapter 9: Apprehension, kill one with the .357 Magnum for this achievement.

Ethically Questionable
Conduct all of the questionable research experiments.


During this chapter there are optional research experiments you'll come across. Conduct all of them for the achievement.



Universal Gravitation
Get killed by your own Snarks.


During Chapter 11: Questionable Ethics you'll unlock the ability to use Snarks as a weapon, they're the small bugs you can throw. For this achievement throw them at the ground and let them kill you.


Futile Resistance
Kill 10 enemies with Snarks.


Similar to the achievement above, however you'll need to kill 10 enemies with the Snarks instead.


Quantum Capacitance
Overcharge it anyway.


During Chapter 11: Questionable Ethics you'll find the Tau Cannon, for this achievement continuously hold the alt fire button (right click) until it overcharges.

Centripetal Attraction
Kill 20 enemies with the Hivehand.


During Chapter 12: Surface tension you'll unlock the ability to use the Hivehand, use it to kill 20 enemies for this achievement.


Stealth Technology
Escape the Hangar in Surface Tension without alerting the Soldiers.


Towards the end of the chapter you'll meet a security guard who you'll need to escort through a hangar, for this achievement you need to reach the exit without alerting the guards. It can be quite annoying as sometimes the marines will spot you / the guard for no reason, I've found the best method is just to stay behind him rather than run in front of him.

Premature Expulsion
Use an entire clip of Gluon ammo in one continuous shot.


Once you've found the Gluon Gun, just keep holding the fire button until you've depleted all of its ammunition.


Hyper Saturation Conundrum
Drown in Lambda Core's coolant.


Self explanatory achievement, you'll need to drown yourself in the Core's coolant, there's a few different areas throughout the chapter where you can do this.




xen when
Wait too long to jump into the Lambda Teleporter.


Once the portal to xen opens at the end of the chapter do NOT jump into it, after around a minute the portal will overload and you'll unlock this achievement.

Orbital Trajectory
Skip the opening Xen island with a secret jump.


Instead of taking the regular path on the left, you'll have to do a jumping puzzle on the right. Video below:



Prolific Popper
Kill all Protozoans in the Borderworld.


For this achievement you need to kill all 64 Protozoans. 37 of them can be found during the Xen chapter, 22 are in the next chapter, Gonarch's Lair and the final 5 are in the last chapter, Interloper. In my video I have also included the locations of the scientists bodies for the Post-Mortem Interval achievement just to make things as easy as possible.



Post-Mortem Interval
Find each member of the missing research teams.


You don't actually start finding the bodies for this achievement until the next chapter, however to make things as easy as possible I have combined this achievement with the Prolific Popper achievement above. There are 7 bodies found throughout Gonarch's Lair. Just like the Prolific Popper achievement you'll need the Cyanogen canister to reach the final body. For the achievement to count you need to interact with the bodies using E, it'll play a faint beeping sound if done correctly!
**According to user m4nu-b4n4nu you can turn on subtitles to more easily tell when you've interacted with one of the scientists bodies!


Nuclear Fishin'
Kill an Ichthyosaur with either the Tau or Gluon.


Ichthyosaur are the fishy aliens that first appear during Chapter 9: Apprehension, however you won't have the weapons required for this achievement. There are a couple different locations where you can unlock this achievement however I found the easiest by far was the cave near the start of the Xen chapter, as the Ichthyosaurs are easy to see since the water is so clear in this area.




Following the Rules
Use the welcome mat.


At the other side of the cave pictured in the achievement above you'll reach the first research area, after turning the power on and opening the first door you'll reach another door with a welcome mat in front of it. For the achievement you'll need to crouch down and interact with the mat.

Gonad Glider
Get whacked into oblivion in the ledge fight.


At the beginning of the chapter you'll need to interact with three of the orange glowing pedestals to start up a machine, a scripted sequence will start where the Gonarch will charge at you, after this just stand still and let it hit you again, you should get knocked off the edge of the map and unlock the achievement. If you try to run to the edge and wait for Gonarch to hit you instead, a lot of the time the achievement won't unlock for whatever reason.


The Plan
Use Cyanogen to kill Gonarch.


In the laboratory in Xen you'll find a canister of Cynaogen. Carry it to the next chapter, Gonarch's Lair, you'll need to place it on a teleporter and then once you light Gonarch on fire and a chase sequence begins, a small path to the secret chamber will open on your left just before you reach the boss fight room. It can be hard to notice if you don't know to look for it. I find the canister and the secret chamber in my Prolific Popper / Post-Mortem Interval video, however I've recorded its own video just in case you need it.



Unquestionably Ethical
Don't use the Cyanogen and let the Gonarch live.


For this achievement you'll need to follow the same steps as the achievement above, however if you don't use the Cyanogen and leave via the jumping puzzle on your left without killing the Gonarch you'll unlock this achievement.


Doctor's Signature
Deliver the finishing blow to Gonarch with your Crowbar.


Once you and Gonarch have fallen to the second floor, shoot it with your rocket launcher a few times then finish it off with your crowbar. There's an autosave right as you fall down, so this achievement isn't too hard.

PhD in Pacifism
Don't kill any Vortigaunts in the Borderworld.


Throughout the chapter you'll see lots of Vortigaunts, all you need to do is reach the end of the Borderworld without killing any of them. Just focus on killing the Controllers and you shouldn't have too much trouble.


Anti-Matter Over Mind
Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.


Controllers are the big brained flying creatures, while doing the PhD in Pacifism achievement above you'll unlock this achievement very easily.


Laser Immunization
Complete Interloper without taking any laser damage.


Throughout the chapter there are lots of sequences with red lasers, as soon as you see one make sure you save, if it hits you just reload. Pay attention to how much hp you have so you can notice if it hits you or not. If you save often this achievement isn't too difficult.


Contest Propellant
Find the snack supply canister.


After fighting off the Controllers a small exit for you to climb through will appear, instead of continuing on however move the boxes on your left and head up the stairs to find the snack supply canister.



Black Mesa Decathlon Winner
Escape the Gargantua’s Lair without taking any damage from Gargantuas.


For this achievement you need to make it through the chase scene in the Gargantua's Lair without taking any damage from Gargantuas. Taking damage from the smaller enemies doesn't matter. If you save at all during this section it will negate the achievement so make sure you save before it loads in case you need to restart.

Specimen GG
Take out all three Healing Crystals in Nihilanth’s Chamber at the same time.


While fighting Nihilanth 3 crystals will appear, to unlock this achievement you'll need to place 3 satchels on top of where they spawn beforehand. Then once the crystals appear and start healing Nihilanth, detonate the satchels and you'll unlock the achievement. For the achievement below you'll need to do this anyway to save time, so you can follow my video for the Late for Work achievement if you're confused.




Late for Work
Defeat Nihilanth in under 4 minutes.


This achievement is actually a lot easier than it seems. My strategy was to immediately place satchels on the crystal stations, use my rocket launcher to destroy Nihilanth's shield beams. Then once you've destroyed the shield, the healing crystals will appear and you can use the satchels you placed earlier to immediately destroy them. After this use the Gluon Gun to finish him off, there's plenty of little canisters around for you to stock up on HP and ammo for your Gluon Gun so you shouldn't have any trouble.

Limitless Potential
Accept G-Man’s offer of employment.


After G-Man finishes talking walk into the portal.


Rather an Anticlimax
Decline G-Man’s offer of employment.


Similar to the achievement above however instead of walking into the portal wait for around 20 seconds and you'll unlock this achievement.