According to Australian standards AS 4343 "Pressure equipment - Hazard levels":
"
Lethal contents are classified as containing a very toxic substance or highly radio active substance which, under the expected concentration and operating conditions, is capable, on leakage, of producing death or serious irreversible harm to persons from a single short term exposure to a very small amount of the substance by inhalation or contact, even when prompt restorative measures are taken.
Very harmful contents are “containing a substance, which, under expected concentration and operating conditions, are classified as extremely or highly flammable, very toxic, toxic, harmful, oxidizing, explosive, self-reactive, corrosive, or harmful to human tissue, but excluding lethal contents.” This class includes carcinogenic, mutagenic and tetatogenic substances.
Harmful contents are “containing a substance which, under the expected concentration and operating conditions, is classified as a combustible liquid or fluid irritant to humans, or is harmful to the environment, above 90
°C, or below –30°C, but excluding lethal or very harmful fluid.
Non-harmful contents are contents not covered by the above categories except for concentration effects such as oxygen depletion and pressure."
See also
(the page is in Italian but very easy to navigate through)
Dejan IVANOVIC
Process Engineer, MSChE