The woman's mother-in-law was convinced that "something was looking at her", however, not everyone was convinced.
"As someone who has spent a lot of time in hospital, most of the vents that I have seen anyways have that silver ventilation tubing," one person wrote.
But others said they could see why the woman thought it was a figure, as the shape "looks like fingers" or a "blonde-haired man".
However several others agreed that it was most likely a possum, with one person saying they had "one peer at me from aircon vents" before.
Whatever it is, we won't be peering into any air vents any time soon.
It's not the only time someone has spotted a creepy detail in a social media post, with a video on TikTok going viral last year after a mysterious shape was spotted in the background.
It's not the first time someone has spotted a creepy detail in an Instagram post. Photo / Supplied
TikTok user Reubix_Cube posted the video of himself busting some moves to Doja Cat's Say So while he says he was home alone.
But social media users watching the clip, which was filmed in a lounge room where stairs leading to the next floor were visible, spotted something sinister happening in the background while he danced away seemingly unaware.
Commenters pointed out a dark shadow that appears momentarily at the top of the stairs, describing it as looking like someone "poking their head" around the corner.
However, not everyone was convinced the video was genuine, suggesting it was staged deliberately to go viral on the platform.
"Obviously this is planned, the caption says 'I was home alone,' (he) wanted us to know," one person wrote.