Air duct cleaning

[Halfathumb]

I'll try to keep this as short as possible. I moved out of my house, a 3 BR ranch, 1700SF on a crawl space. Over the years we had 10 cats, we're trying to sell it but cat urine odor prevails. The realtor thinks the smell is coming primarily from the air ducts. He says this because the cat room is a good distance from the kitchen where it can be smelled also. My question is, can a good cleaning of the air ducts remove the odor? Or does the duct work need to be replaced? FWIW, there are 17 air ducts.

Also, when interviewing someone to do the cleaning, what questions do I need to ask them as to what they do for the money?

Experienced information is greatly appreciated.

Jim

[lift mechanic]

Couple of questions, 

What are the ducts made of metal or insulated flexible duct? Metal could be cleaned.

The crawl space probably dirt, did the cats have access to the crawl space? If they did they may have used the area for there toilet. I have used Nature's Miracle to remove small cat/dog accidents.

[blackhat]

A standard duct cleaning should remove any material that’s trapping odours. If it’s all metal duct, it can be conventionally cleaned and then chemically cleaned. 2 schmucks in a truck duct cleaning probably won’t do chemical. You’ll be looking for an outfit that does commercial/industrial jobs. Ask your insurance folks who they recommend for disaster remediation and then ask who they use.

[EatenByLimestone]

I had some renters who failed to let their dogs out. Back a zap sprayed on the troubled areas really helped eat the smell. I still ended up sealing the hardwood floor with shellac based primer.

[Halfathumb]

The ductwork is flex. The cats never had access to the crawl space. I just contract for a thorough cleaning with an Heme Halo attached to the HVAC system. $2500, if this doesn't work anyone know of good arsonists?