These modules are low current and are tradionally used to plug in and populate/condition the 4 to 16 module I/O boards used with μp type I/O.
I am not sure if you can get the Opto22 where you are but there are equivalent stand alone units that go to 25amps.
You can get zero switching types.
The components are not dangerous. Apparently somebody is assuming you aren't able to assemble them correctly.
Well, of course the safer the better.First of all it is big deference by playing with a 5 volt Arduino setup and construct something that is made to be connected to mains. Every unit that are made to be mains connected have to be approved and apply to a set of regulations. If this approval is missing your setup will not in any country be legal for mains connection. Let us take a bad scenario I am not saying it will ever happen to your hatchery. Your house get badly fire-damaged and the cause is your home made hatchery. Then your insurance company trace the cause of fire to your home made hatchery(and oh yes they will). They will say sorry but the fire was started by your negligence and we will not pay you a dime. You used non approved equipment have a nice day. I know you will probably go ahead with your project anyway. IF you use a proper SSR mounted correct. This device will at least have been subjected to some approval. And be a tad more safe than your bread board mains power controller. Perhaps more important is how you mount your heating elements. But is is also a lot of other pitfalls with your project. That you may not know about.
Would something like that http://www.ebay.com/itm/Solid-State...Electrical_Test_Equipment&hash=item53ef7abdd9
be safer to use?
And about the heating elements i know that i need to place them properly, fixed, and mounted with isolated material.
And i'm going to connect a fuse 1/2A (the current in the circuit is 0.2A) so in case that there would be any shortcut it won't catch on flames. (the electric board in the house has 16A limit as well)
Waiting for your comments.