Using Thiomyl (Cleary's Generic) Indoors
 

Ive read the label multiple times and the closest I can get to indoor application is "well ventilated area". Otherwise, it says to use outdoor, which probably isnt great because my only outdoor access is a balcony on the 12th floor of an apartment, so drainage would pose issues to everyone beneath me.

Of course, it was never designed to be for indoor use, but does anyone here have experience in using Thiomyl on their indoor collection?
If so, how did you go about it and take precautions?

It's unlikely you have a fungal infection in your plants treatable with thiomyl unless your growing conditions are hot and very humid. Look for other causes of your plant's problems.

Fungicides are usually toxic to humans, too.

Is the black rot I was trying to resolve unaffected by Thiomyl? I have been waiting for Phyton 20 to arrive and wanted to just treat the adjacent orchids to my black rot plant with a systemic as a preventative measure

You don't know what is causing the black spots. It might be a fungus but that's unlikely. There are many different pathogenic fungi. Not all are killed by every fungicide. Before using a fungicide you need to know which fungus is causing the problem, and you need to know the fungus is killed by the fungicide you plan to use. If you use a fungicide that's not effective against a fungus it will still kill beneficial microorganisms on the plant, organisms that may keep pathogenic fungi in check.

Can you post some photos of the plants you want to treat?

First is the plant with black rot, second is the divided plants after I performed surgery down to the rhizome.

Third photo are the plants I want to treat as a preventative since they were in the same watering tray as the infected orchid.

I'll let others suggest any treatment, not an area of expertise, under my growing conditions I don't have much in the way of rot problems. But lesson learned, I hope... Don't share water between plants!!! That's just asking for shared diseases!

Is it considered water sharing if I take the grates out of the trays and water all orchids in one go from the sink? The water cannot pool that way I'm not reusing any water, but I believe water will splash between the leaves as water hits it.

Am I not supposed to group plants together? Or simply just water each orchid separately off of the grate?
I've always grown with my orchids clumped a bit to allow them all to fit under the lights and keep relative humidity higher

In a perfect world (one with an infinite amount of space to give each orchid a "buffer) it would be ideal to have them not touch each other or splash water between. Not practical... no matter how big one's growing area, it fills up. So it's probably not possible to avoid drips and splashes. I suspect that the odds of cross-contamination are probably fairly small. What caught my eye was mention of "same watering tray" which to me implied that they might be sitting in shared water which would greatly increase the odds of cross contamination. I'd suggest leaving the grates in place, when you water, it drips into a "catch basin" or tray but what drains through one plant isn't picked up by another. Then you can dump the catch basin at the end of the process.

The setup that I used when I did some growing under lights (my spare bedroom was my "greenhouse" http://orchidcentral.org/GrowingAreas/indoor.jpg , the pans were pretty big, I just watered with a pump sprayer, it ran through the plants, eventually just evaporated (raising humidity). I'd clean out the pans about once in 6 months when they got too icky with algae.

Ah, okay, so everything I have been doing with my watering is pretty okay then! Sorry for the confusion, my wording wasn't very clear.
I dont water my plants in the tray, since its hard to pour anything in the shelf. I take the grates out of the tray and water them all in the sink where they freely drain and then I plop them back on top of the tray. Instead of the used orchid water, I use fresh distilled water in the tray basin for added humidity. The orchids all sit on grates 2 inches above the water as well.

If cross contamination risk is low, then I would probably only attempt the use of the thiomyl on the one infected plant. But that would only be my course of action if it actually treats black rot and if I can find a way to use it in a proper fashion without poisoning myself or my pets