coolfun 125,
i also encountered poison gas in my ongoing project,its color white and placed in cement container. before going thru poison trap you will encounter poison markers like biting animal, dog,snakes etc. in my case,we bypass the 1st poison placed in an oblong shape cement container. the 2nd time,we got markers 5 ft before we hit poison. we apply blower fan to neutralize, the toxic remains but the diggers can manage the itchy smell and watery eyes. my mentor,before he died, is using japan made poison anti dote.its like a detergent soap mix in water and apply to the area and it will penetrate the poison soil at 4 ft. he also encountered lots of poison trap,the most lethal is liquid form in bottles ,as of now only 1 kilo anti dote were left. i also use activated carbon/charcoal and its also effected. try google activated carbon for more info. the best thing is used gas mask for better protection.
regards to all