Carpet & upholstery freshener

Baking soda infused with essential oil or dried lavender, sprinkled on rugs and upholstery and vacuumed up to lift odors.

Keep pets and children off treated areas until they've been thoroughly vacuumed. Cats especially are sensitive to essential oil residue (tea tree, citrus, peppermint, eucalyptus).
Spot-test on a hidden area first, especially wool, silk and delicate upholstery, because oil can mark some fibers.
Fine powder can clog bagless vacuum filters. Empty the canister and clean the filter afterward.
If you also spot-clean the carpet with other products, never combine bleach with ammonia, vinegar or other acids, or rubbing alcohol, and never mix hydrogen peroxide with vinegar in one bottle.
Don't use on damp carpet. It turns to paste.

Steps

Whisk the baking soda and cornstarch in the bowl.
Add the essential oil a drop at a time, whisking and breaking up clumps with a fork as you go.
Stir in the crushed dried lavender, if using, and sieve the mix so it's fine and even.
Put it in the shaker jar and let it rest, sealed, for 24 hours so the scent spreads through it.
Spot-test, then shake a light, even layer over a dry rug or upholstery.
Leave it for 15–30 minutes, or overnight for strong odors, with pets kept out.
Vacuum thoroughly, going over each area several times, then empty and clean the vacuum filter.

Clumping powder: Oil added too fast or humid air. Add oil drop by drop while whisking, sieve the mix, and store it sealed with the cornstarch.
White residue left in the carpet: Too much powder or not enough vacuuming. Use a light layer and vacuum slowly in several directions.
Odor comes back: Baking soda absorbs surface odors only. Deep-clean the source, such as pet accidents, with an enzyme cleaner.