Since markers are among the most important office supplies, they should be very safe items to use. Our markers do not have strong odor or contain substances harmful to human respiratory system (Xylene free). The ink that we used have had a toxicological evaluation by an established laboratory to contain no material in sufficient quantities to be toxic or injurious to human or to cause acute or chronic health problems according to the requirements of the European Union’s CE EN-71/3 and American’s safety standards ASTM D-4236.