I have always had great luck with baking soda. Seal them in a bag or container with plenty of baking soda. There is also smoke removal products available. I have had good luck with this one too https://www.amazon.com/Fresh-Wave-Odor-Removing-Gel/dp/B000I9QJ5S/ref=mp_s_a_1_27_mod_primary_new?crid=3R3Z7015MNBYT&keywords=smoke+remover+for+home&qid=1666412642&qu=eyJxc2MiOiI1LjIyIiwicXNhIjoiNS4wOSIsInFzcCI6IjQuNzQifQ%3D%3D&sbo...
We have had our litter robot since February. I haven't changed the carbon filter yet. We use tall kitchen trash bags as liners. The litter you use does make a big difference. We switched to litter with charcoal and sprinkle some litter and baking soda in the waste tray bag to absorb the odor.
This all helped a lot but the biggest smell reduction was made by putting a jar of Fresh Wave Odor Removing Gel inside the waste tray (the tray has a big gap between the carbon filter and the liner). People really love these gel air fresheners. They're a tad bit pricey next to other options but work really well.
I guess - from what I’ve seen and read from others - this is what is amazing to put in the waste drawer in the front by the carbon filter
Fresh Wave Odor Removing Gel, 15 oz. (Pack of 2) https://www.amazon.com/dp/B000I9QJ5S/ref=cm_sw_r_cp_api_i_EEA4ZDQY4FDTSQPR8EKR?_encoding=UTF8&psc=1
I have a 4” in-line fan with the corresponding ductwork/ carbon filter in my 2’x2’, and to be extra safe on top of that I have a few of these around that room Fresh Wave Odor Removing Gel, 15 oz. (Pack of 2) https://www.amazon.com/dp/B000I9QJ5S/ref=cm_sw_r_cp_api_glt_fabc_7T3RPNA4CN01CT2S31ER?_encoding=UTF8&psc=1
Ask them what stink they're trying to cover up? That's all I can think in scented houses, like what nasty are you covering? Lol
I hate scents, too. I found an air freshener gel that works by removing stinks rather than adding extra crap to the air. It has a light natural scent that is barely noticeable. Maybe they'd be willing to switch to it? It's fabulous and does what it should. Fresh Wave Odor Removing Gel, 15 oz. (Pack of 2) https://www.amazon.com/dp/B000I9QJ5S/ref=cm_sw_r_apan_glt_fabc_15BSGVR080JF142N31C1
There's a few sizes and refill jugs, too.
If they say they like the smell then maybe you can see if they'll just use it in their room and not the common areas. Fingers crossed for you!
There are some products that absorb odors - they are usually a gel or beads that absorb. It could help a lot. I use lavender ones.
I use these, Fresh Wave Odor Removing Gel, 15 oz. - Special Value 2-Pack https://smile.amazon.com/dp/B000I9QJ5S/ref=cm_sw_r_cp_api_glc_fabc_As07FbYXS2NFD?_encoding=UTF8&psc=1
i put weather sealing adhesive plastic strips around the existing carbon strips, at the opening to the bin. this creates a tighter seal and prevents odor from seeping out.
i also put duct tape (black gorilla tape) on the inside of the bin to block the air vent (where the carbon filter is located. removed the carbon filter first). this is the main place smell seeps out of.
and inside the bin itself, in the space beside the carbon filter, i placed one of these smell removal gel jars. they smell like ointment at first but after 2 days have no smell and totally neutralize the litter smell. https://www.amazon.com/Fresh-Wave-Odor-Removing-Gel/dp/B000I9QJ5S
I don't like to 'cover' odors, but I found placing one of these in the drawer (in between the filter and the bag) helps immensely: Fresh Wave Odor Removing Gel, 15 oz. (Pack of 2)
Throw one of these in the drawer https://www.amazon.com/dp/B000I9QJ5S
It's not 100% eliminated but better than any other litter box I've used.
I put one of these in the drawer and it makes the smell like 99% gone: https://www.amazon.com/dp/B000I9QJ5S
My husband is EXTREMELY senstive to smell.
I use this product in the container:
https://www.amazon.com/Fresh-Wave-Odor-Removing-Gel/dp/B000I9QJ5S/ref=sr_1_5?crid=TQQXUNEPUXXV&keywords=fresh+wave+cleaner&qid=1644922662&sprefix=freshwave+cleane%2Caps%2C123&sr=8-5
And I would also suggest one of the following products to wipe down all the plastic surfaces with (please not, these are not cleaning products but deoderizing products. They will not disinfect or clean the surface, but should remove the smell. In suggest cleaning the surface first then using these products):
https://www.amazon.com/Fresh-Wave-IAQ-Commercial-Eliminating/dp/B005H0JNXI/ref=sr_1_11?crid=TQQXUNEPUXXV&keywords=fresh+wave+cleaner&qid=1644922662&sprefix=freshwave+cleane%2Caps%2C123&sr=8-11
OR
https://www.amazon.com/ANGRY-ORANGE-Ready-Citrus-Eliminator/dp/B07N316V8C/ref=sr_1_8?crid=SL5NOEN0LIED&keywords=animal+odor+remover&qid=1644922802&sprefix=animal+odor+remover%2Caps%2C124&sr=8-8 (Not suggested for inside of globe due to its strong smell)
I foster kittens and understand how much they can stink! I have had good look with this odor neutralizer. Fresh Wave
I stick one of these down in the litter drawer (right behind the filter). I curve the bag halfway over it to prevent litter from falling in. Works great.
Arm and Hammer litter and one of these inside the tray: Fresh Wave Odor Removing Gel, 15 oz. (Pack of 2) https://www.amazon.com/dp/B000I9QJ5S/ref=cm_sw_r_apan_glt_fabc_CEW0B9D3JHRAHTGP41MA?_encoding=UTF8&psc=1
Smell gone for me.
I put this in the litter compartment box in the front near the filter. No smell issues.
Try a different litter. What are you using?
Also: I swear by these. Put one of those in the waste drawer underneath the bag, they last about 2-3 weeks each and they actually do a hell of a job of nuking any smells lingering.