I mixed up a fresh batch of XTOL last night in my darkroom, and after adding Part A (Phenidone+sodium sulphite) to the 31degC pure water then mixing for 5 mins, I had a sudden bout of diarrhoea ! I was wearing this gas mask with TWO of these organic gas filters, plus goggles and gloves. I had my extraction fan plus ducted air-conditioning ventilation going full speed. Despite all my precautions I got mucosal irritation in my nose and throat and then diarrhoea ! I'm assuming the gas being liberated and inhaled was sulphurous acid. Both symptoms are documented side effects of exposure to sodium sulphite and sulphurous acid. Clearly I need to do this in either a fume cupboard or outside again (like I used to).