How long can you store red fox urine in a dark place and still have it good to use at fox and coyote sets?

Till it starts to stink like ammonia.

If it was good urine to begin with, it should keep indefinitely

I have some --2020 SMC urine That I caught a coyote with today.

I still have some coyote urine I bought from O'G way back in 1989 Still smells the same as the day I bought it.

Well, that wouldn't take very long.
Take the lid off and it will dissipate

Ammonia is a welcome smell . When it smells like sewer gas, dump it .

I have some that I bought from Wayne that’s probably ten years old , still smells like coyote pee .

As stated many times over, ammonia is a natural developing odor in all stored urines in time. The stronger the uric acid content in the urine, like meat fed animal urines, they will develop a very strong ammonia odor in short order once the urine is contained and sealed. Cereal, meal, dog food, and marginal diets fed to penned animals will produce very little ammonia odor over storage. The time of year the urine is collected plays a big role also. Good clean urine will remain good, indefinitely.

Bob, are any additives used to help preserve the integrity of the urine or is it just straight urine?

That is a good question beaverpeeler. There are some urines jugs or batches that may show signs of some early signs of bacteria development after receiving it.

Other batches that have been well handled in the collection process would be fine. We always take the precaution to filter all urine 2X times. We use 190-micron filters for all of our received or collected urine. This will remove any particulate solids or insects that may have been missed during the producers filtering / straining process.

Well-handled urines from a clean operation need no additives. I would venture a guess that everyone that buys much urine gets some questionable urine from time to time. Experience in knowing what you are getting is key. Dirty / soured urine cannot be recovered and should be given back or sold at a discounted price. It can still be used but it certainly isn't #1 grade.

No amount of preservative/ or additives will bring back contaminated urine. Preservatives can stop the bacteria from multiplying beyond that point but that is all it can be expected to do.

The process of pasteurization is heating the urine. That would eradicate the bacteria completely without any necessary additives. However, you will lose some volume in the heating / evaporation process. I did that once many years ago to become familiar with the process and its affects. I likely will not do that again.

I had about 8-10 gal of fox urine that I had set aside from over the years that I wouldn't sell. So, I was bored one day, and I wanted to try the pasteurization process since I had little to lose in terms of investment.

After pasteurizing the urine, it was filtered again after cooling. There was a slight sludge layer in the bottom of the pot that had settled out during the pasteurization process.

It was an interesting experiment. Even though the urine was pasteurized with respects to bacteria content, it did not change the urines final odor.

I kept an original pre pasteurization urine sample for comparison. Over the years I used this urine up on the trapline very liberally at bait stations and drilled hole scent posts.

Very informative Bob. That you for that. Would 190 microns be about like a coffee filter? But presumably bacteria if present could still pass through?

The information I have on coffee filters indicates that paper fiber filters have 60 - 100 microns in their perforation size. No filters will remove bacteria microbes to my knowledge. That is why I stated if urine is contaminated with some feces, blood/food particles etc., the bacteria will continue to multiply over time.

You can stop it with the right preservatives but you won't reverse it as to its current state.

Coffee filters will take out most of the smaller particles, but they are not at the 190-micron size. You can get those filters from your local NAPA store, or you can buy them online also. We buy in bulk since we use so many filters. I believe they use those filters for straining paints and solvents for prepping paints for painting vehicles.

Yes, they use them for paint. You can get them at any place that sells paint you can use in a spray gun. In fact a lot of your paint stores give some to you with any purchase of a paint like an auto paint. I had some around from painting an old pickup. I Tried straining some fish juice through them. That didn't work too well, got nice clean fish juice, but the filters were too fine, it wouldn't hardly flow through it, take all day to do a quart. Must be thicker than urine. lol

Only the pourable fluids can be used in those 190-micron filters. The more solids that are in the fluid the faster the pores will plug up. In years past I used old and even bought some panty hose and stockings to strain fish oil and other fluids that I needed to clean up. They did a decent job. Fish juice can have lots of debris depending on the fish and how it was handled.

Pouring thru a 1/4 " hardware mesh funnel first will remove much of the larger material. Then pouring it thru some large mesh bags will hold the solids and allow the fluid to perk thru. They sell large 5-gallon bucket mesh netting that will line a bucket. I keep lots of those on hand. They are reusable if you are careful in how you handle them and rinse them out well.