If you come across a note from a flight attendant in your hotel room, you might want to call housekeeping.

People often wonder if hotel sheets are as clean as they look — and there’s good reason to question it.

Despite occasional lapses in daily housekeeping, one would anticipate the bed sheets to be replaced between guests, which is not always the case.

Flight attendants probably spend more time in hotels than most other people and have likely been exposed to a wide range of standards. For example, crew members will often pull back bed sheets as soon as they arrive at a hotel to check for bedbugs — and if they’ve even been changed.

And since they know what to look for, flight attendants are trying to warn future guests about the cleanliness of their linens with a simple note.

Flight attendants have started to tuck a note into the linen on hotel beds to let future guests know that the sheets they’re about to sleep in haven’t been changed, Paddle Your Own Kanoo reported.

The note will likely be on the hotel’s stationery and say something like, “If you find this note, then this bed still has its old sheets on.”

If you find one of these notes, PYOK suggested taking one of two routes: either request a new room or ask housekeeping to change the sheets.

However, if you ask for a new room, you run the risk of getting another bed with unchanged sheets.

Flight attendants will sometimes make a stain on the sheets when asking housekeeping to change the sheets to make sure that the request will be acted on as soon as they arrive.

Meanwhile, some flight attendants don’t even risk it and pack their own set of sheets and pillow covers so they don’t have to touch the linens on the hotel bed.

In general, hotel comforters are only washed at most every few months, decorative pillows are never washed and fabric runners at the end of the bed should be avoided as well.

PYOK recommended immediately discarding the decorative pillows to a nearby seat or sofa.

As for the fabric runners, they act as decor but hotels also put them there because it’s known that guests often put their suitcases at the end of the bed when they first arrive — so while it protects the bed and sheets from getting dirty, they are also a home to germs from the suitcase.