What is a strong disinfectant?

A strong disinfectant is a chemical agent that kills a broad spectrum of microorganisms including tough bacteria like tuberculosis, viruses like COVID and norovirus, fungi, and often bacterial spores, with fast kill times and EPA registration for hospital use. Examples of strong disinfectants include bleach, sodium hypochlorite at 1000 to 5000 ppm, which is considered one of the strongest readily available disinfectants because it kills almost everything including C. difficile spores when used with proper contact time of several minutes, though it has strong fumes and can damage surfaces. Another strong disinfectant is accelerated hydrogen peroxide like Oxivir which kills TB, MRSA, and norovirus in 1 minute and is used in hospitals for operating rooms and negative pressure isolation rooms, breaking down into water and oxygen. Peracetic acid and chlorine dioxide are even stronger sporicidal disinfectants used for sterilizing medical instruments and for terminal cleaning with vapor systems that fill entire room. Quaternary ammonium compounds at hospital concentration are strong for daily use with low odor. Glutaraldehyde is very strong for instruments but toxic for surfaces. Strength depends on concentration, contact time, and whether surface is pre-cleaned, as dirt reduces effectiveness. Strong disinfectants require PPE like gloves and masks, good ventilation to avoid lung irritation, and should not be mixed with other cleaners. For home use, strong does not always mean better, a moderately strong hydrogen peroxide disinfectant with good cleaning first is often best balance of effectiveness and safety.