Things to be aware of when making a DIY macro lens using ZnNSe

[TUKIKAGE]

ZnSe lenses are the less expensive of the infrared-transmitting lenses, but before purchasing one you should check your local laws to see if there are any regulations regarding how you should handle them and whether you can dispose of them properly yourself.

ZnSe optical Lenses
Inhalation of debris or dust can be toxic and can accumulate. Contact with gastric juices releases highly toxic hydrogen selenide. Prolonged contact can cause dermatitis.
Harmful gases are also produced when exposed to acid or high temperatures.
washing hands after handling ZnSe to avoid any transfer of ZnSe dust into themouth from handling food, etc.
Broken or scrap ZnSe pieces should be disposed of in a properly licensed industrial disposal facility.

In my country, AR-coated lenses can be purchased without any restrictions on being toxic, but when disposing of them, they are treated as toxic substances and a high disposal fee must be paid to a special company.
Additionally, it can be difficult to find a waste disposal company that will deal with individuals.

[Gary350z]

Interesting bit of information. I have a ZnSe lens used for a thermal camera.
I did a quick online search, and it seems to be true. The search results say the danger is from mild to bad. How bad is it really. I don't know. I only spent a little time searching.

[TUKIKAGE]

I'm not an expert, but looking at SDS and the example of the fire at the selenium rectifier factory, it is rare for irreversible symptoms to occur, and with the appropriate knowledge, I don't think the toxicity to the human body is something to be feared.

Mercury is contained in common products used by the general public, so there are established routes for disposing of these, but selenium is not expected to be handled by the general public, and the lack of a route makes it difficult to dispose of.
Swollen lithium polymer batteries are also cursed items that are difficult for individuals to dispose of correctly if you try to follow the rules.
Some manufacturers will take back lenses if you send them back when you dispose of them, but only if they were purchased from that manufacturer.

That is the situation under the laws and rules in my country, but what are the rules in your country?

[mzzj]

That is the situation under the laws and rules in my country, but what are the rules in your country?

Over here you would just Attach label telling what the material is and leave to household hazardous material disposal (free of charge.) drugs(medicines) would go to pharmacy and explosives to police.

Selenium is also not as poisonous or ”undesirable” like lead for example. (Tiny) bit is needed for animals including humans. Over here selenium is added to infant formula and fertilizers as the selenium levels in soil are low.

But one ZnSe lens contains probably million-fold amount over recommended  daily dose of selenium.