That's okay. It's probably fake.

While you still had most of your supply of Manacite, you had no idea how potent 20 vials were, or how far they could spread. Thankfully it would remain in the building, but your real issue was with the warning you read in the letter:

LACK OF A VERBAL COMMAND COULD RESULT IN ANIMATED OBJECT BEHAVING UNPREDICTABLY.

You didn't really get how a powder could "understand" a verbal command in the first place. The whole mailing was probably a gag, and the Manacite wouldn't do a thing. You looked back at the grate one more time before continuing to your apartment. When you got to the door, though, you had an idea.

You'd put this whole thing to bed right now. This magic powder had to be bunk.

You carefully opened the box again, pulling out a single vial and twisting the aperture top just enough to let a few grains of the red, crystalline powder out. You took the 'Tomorrow Industries' letter, folded it down the middle, and made a kind of paper slide that you pressed against the lock cylinder.

"Nice and smooth..." you whisper as you tap out a little of the powder. The red crystals fall--the largest of the grains descending into the lock cylinder itself as the smallest, dust-like particles leave a residue on the paper. You sigh. "Okay, let's go. Unlock."

You smirk after a moment, knowing nothing was going to happen. As you dig through your pocket for your door key, though--you hear the bolt. You look up just in time to watch the cylinder turn over.

You gasped, looking back at the red-dusted letter and reading the warning one more time:
LACK OF A VERBAL COMMAND COULD RESULT IN ANIMATED OBJECT BEHAVING UNPREDICTABLY.

As the paper itself started fluttering, you gripped it tighter and spat something out.

"Um, um...fold into a paper airplane!" That seemed harmless enough. "Snub-nosed."

When you let the paper go, it lifted into the air and began creasing itself, folding and unfolding, going through all the motions you'd do yourself to make the plane. It sat in the air, hovering as it slowly rotated--as if it was showing its own work off.

"Holy shit. I mean...holy shit." You grabbed the floating plane and looked at it. "F-fly down the hall, swoop up the window at the end, and then, like...fly inverted along the ceiling until you get back to me."

The thing sailed out of your hands. Unlike its eerie hovering, the flight of the paper airplane seemed to use the air resistance to its advantage, and you could actually see the paper plane bending and twisting through its vertical climb, straightening its flaps again as it sailed along the ceiling.

You wondered how in the hell this could all be possible. Down to the detail of your flight plan, the paper airplane followed your instructions with perfection. You looked at your door again and smirked, popping the vial open a little and letting a crystal or five drop on the knob.

"Open up. Let the plane and I in, and then close...and lock." You feel absolutely giddy as you say the words, watching as the knob turns on its own. The door swings open, and you walk in. You turn back to command the plane, but it follows you in without a specific direction. Once you're both clear of the threshold and away from the door, it closes and locks.

Having confirmed the authenticity of the Manacite, you felt a rush of awe. All the crazy things you could try with this substance...

And the thought was stopped dead when you looked back at the paper airplane, seeing the print on the underside of the fuselage:

-LD RESULT IN ANIMATED OBJECT BEHAVING UNPREDICTABLY.

The twenty vials in the air ducts were absolutely trouble. At the very least, the duct system itself was already affected. You had no idea what the HVAC system would do on its own. Maybe nothing...