Odors get trapped in my stair well. What can I do?

Buy a gallon of cheap vinegar. Pour it in buckets and leave on the stairs. At first the vinegar will smell strong. But after a day or two there is no smell at all.

What stair well? Where? Please provide moore information on the details of your stair well.

Christierei's vinegar idea will be helpful, but you still have to find the source of the smell. Is it in your own home or do you live in an apartment? Could it be coming from a dead animal in the walls? Is there a pile of wet or moldy rags somewhere? Could it be coming from another apartment? You really need to find the source before you can fix it permanently.

If the reason for the smell is that house cooking, etc. just waft there and there isn't enough air movement to push them onward, thry some sachets with cedar shavings, or carved cedar cut outs for decore or attractive jars or bowls with baking soda in them to absorb the odors.

Apple cider vinegar is a good odor neutralizer!