Use sulfide toners such as Kodak Brown Toner with good ventllation. The rotten egg smell is hydrogen sulfide, a poisonous gas. Make sure the toner solution never comes in contact with acids even weak ones. Hydrogen sulfide is especially dangerous since it first dulls the sense of smell even at low concentrations. Then the amount of gas can reach a toxic level without being detected.
The concentrate and solutions are very alkaline and can cause burns upon skin contact. Wear protective gloves.