What Does the Smell Mean?

to your question:

In relation to the story, the smell only shows her progression towards insanity. First she is bothered by sight, which is the movement of the wallpaper and now is the smell. Her mind has completely overpowered her senses making her believe these things. When a person is leading onself towards insanity, the mind has the power ( tools ) which are the senses.

the smell was only of her creation just like everything else. it doesnt symbolize anything just compares the reation of the color of the paper as now whe says yellow smell.

I don't believe the smell is imagined for it was most noticeable during mosit and muggy conditions. It could be urine. Along the parameter of the room, excluding the bed there is a "smooch." This "smooch" could very well be urine from a time ago by men or boys marking their territory. The description of the room could have been a housing place for someone of mental disorder.

Remember she has "carved" her shoulder into the plaster as she creeps along the circumference of the room. She's in her nightgown and the yellow from the wallpaper coupled with urine and the moist night air humidity has created the smell. Also she has not bathed in quite some time. The walls themselves are absorbing her sanity and the physical manifestation of this is the smell.