The containment chamber must have an airlock installed with one door closed at all times.
Containment at all times is already assumed. Readers, both in- and out of universe, will assume that a particular action in the containment procedures should be continued unless you specify otherwise.
Although made of copper, no tarnish and oxidation are not present.
It is always stronger language to describe what something is than to describe what it isnot.
SCP-XXXX cannot form into a structure that is bigger than the space of which it occupies.
Why was this sentence underlined?
In this aggressive state, SCP-XXXX will posses any living organisms around it.
The word "possess" feels unscientific and even inappropriate in this context. I feel like this sentence could be eliminated since you imply this with the description later anyway.
Through means of which are not known, SCP-XXXX will enter the host via an orifice, including but not limited to the mouth, ears, nose, [DATA EXPUNGED], or [DATA EXPUNGED]. It will then proceed to completely consume the skeletal structure of the host and replace it with itself (The host is hereafter referred to as SCP-XXXX-1).
Since the host can be from any entity that enters containment, it would be more appropriate to call them "instances of -1" instead. This goes for all other points where this crops up, but for brevity, I will only correct it here.
No traces of bone are ever found in SCP-XXXX-1— leading researches to believe that SCP-XXXX "deletes" them from existence—.
Definitely leave this part up to the imagination. What the reader imagines will always be scarier, and it omits the issue of what the scientists "believe" happened instead of recording what actually happened.
SCP-XXXX-1 is capable of speech, however, though with a reduced vocabulary.
Improper use of however as these two things do not directly contradict each other.
SCP-XXXX-1 has reportedly tried to deceive researchers into thinking that it is normal in an attempt to be freed.
Comparisons to the more well-known SCP-035 aside, I get this hilarious mental image of an instance of -1 banging its hands on the containment door (making a hollow metallic sound) and yelling "Let me out, fellow humans! I must escape before the crafty and extremely handsome copper tubing returns!" This also feels like a sentence that could/should be cut, if for no reason other than brevity. We know it's trying to escape. How it tries doesn't really feel relevant, especially if it's little more than "hey let me out, bro".
Regarding the interview, I infer that Dr. Ph is speaking directly with the skip while Dr. E is above somewhere in an observation booth. Otherwise, it feels odd that Ph and the skip would interact with each other but neither would acknowledge the presence of the third character. If he is supposed to be in the room with them, have one or both characters interact with Dr. E. If not, make that clearer above.
Also, why does it freeze when it does? I initially guessed it was because it exited a host body, but then it did that without freezing during the incident. Clearer rules about what it is able to do and why would help a great deal.
