After searching the forum it is easy to find information on obtaining potassium chlorate from domestic bleach, but I would like more information on the hazards involved in this process. Is it generally necessary to wear a respirator?

I have read that domestic bleach will release HCl gas (and chlorine) when it decomposes upon heating. Is this only true when there are certain contaminants present, or does it occur beyond a certain temperature?

I've been told that you shouldn't let bleach actually reach boiling point (which I gather is close to 100 degress celcius). Is this true, or can you rapidly boil it down as fast as you like?

MetalHead, I've never known bleach to release HCl upon boiling. Some chlorine is
released but if you have adequate ventilation this shouldn't be a problem. I've
used the bleach boil-down method although I prefer electrolysis of chlorides.

After all the hypochlorite decomposes to chlorate, you shouldn't notice the bleach
smell(chlorine) any more. BTW, you have to boil the bleach to get the volume of
the liquid down to at 1/7th or less of your original volume.

3NaOCl ---> NaClO3 + 2NaCl
NaClO3 + KCl ---> KClO3 + NaCl

Have a look at http://www.frogfot.com/synthesis/chloratetherm.html

Frogfot gives simple and easy to follow step by step instructions on how to
make Potassium Chorate out of bleach.
Don't miss the link on the bottom of his page, ah here it is:

http://www.wfvisser.dds.nl/EN/chlorate_EN.html

In some countries it's really difficult to find Potassium Chlorate. Whatever route you take, the bleach method is the route wich gives you the poorest yield.
Try the conversion of Sodium Chlorate with the help of Potassium Chloride. That one is better.

Edit: I made a mistake. Corrected the error.

You will get much better results if you use hypochlorite solution or powder for swimming pool water treatment which you can get as HTH brand from swimming pool supplies.

Household bleach has usually hypochorite concentration below 5% so you get meager yields. The swimming pool stuff has a much higher hypochlorite content.

Agreed, Ca(OCl)2 is much better. This is due to the fact that it can be had in solid
form. Potassium and sodium hypochlorites exist in aqueous solutions only. Many
popular pool bleaches use C3Cl3N3O3, or trichloroisocyanuric acid. You want
calcium hypochlorite which is conveniently sold in 1 LB bags as pool shock. On my
last trip to Walmart they had plenty in stock. Check the ingredients on the bag or
container for the hypochlorite and compare brands if possible for the highest amount
of available chlorine.