You can start FNAHC by choosing it from the Steam Workshop menu via the new UI. If you're using the old UI, you would need to enter hc_fivenights into the command console. It won't start after beating the main Hazard Course.

FNAHC does not start automatically unless you choose it in the menu or load it via console. It does not load after beating the main Hazard Course. It's just an optional add-on that's separate from the rest of HC.

Even if you did accidentally start it, the jumpscares don't start until at least a solid minute or two after the level loads, so you have plenty of time to exit it.

ok, that's a relief.

Wait what's FNACH? It's a horror game or what?

Five Nights at the Hazard Course. Its quite literally Five Nights at Freddies in Half Life.

As stated, you start it by selecting Steam Workshop > Hazard Course > Chapter 3 FNAHC on the main menu.

You control the doors. Look at cameras. Manage your power. Put a mop bucket on your head to hide. A mix of FnaF 1 and 2.

Which I am finding impossibly hard so far. There seems to be no cue for the attacks and they are lightning fast.

引用自 Venrez：

Which I am finding impossibly hard so far. There seems to be no cue for the attacks and they are lightning fast.

There are plenty of cues for all attacks that occur. I recommend reading the FNAHC FAQ (linked in the Workshop item description) for more information.

Like how could you make an fnaf game out of black mesa? WELL ♥♥♥♥...... Hazard Course managed to do it
Welp Purpere for actual unforeseen Consequences