sickness could begin. However, for one caught in the open outside this ~3-kilometer radius from ground zero from a 1-megaton weapon, ducking and covering would drastically increase one's chance of survival, as at this range the radiation hazard is near zero, whereas that from the blast is a chance of 50% fatality at a ~7.5 km range and that of thermal effects 11 km. If someone was caught in the open, and by surprise, by the same 1-megaton weapon detonation, but ducked and covered in 2 seconds time from first noticing the moment of flash, then that person would have prevented themselves from being exposed to the full brunt of the 1-megaton explosion's thermal energy; instead, approximately 55% of the explosion's total thermal flash energy would have been absorbed over these 2 seconds. In this example, as there is now a 45% reduction in the amount of heat experienced by one ducking and covering, the median lethal thermal range from this 1-megaton weapon can now be more accurately described as equivalent to absorbing the entire flash energy from a 0.55 Mt or 550 kt weapon, if one ducks and covers in 2 seconds. Hence, one's chance of survival at 11 km goes from the previous 50% chance of death if they just stood there, gazing at the 1-megaton fireball as it emits all its energy over tens of seconds, to now a mere sunburn, or a 1st-degree burn injury on exposed skin. With the 50% lethal thermal range being thus downrated to being equivalent to a 550 kt explosion, the 50% lethal thermal radius goes from the previous 11 km without ducking and covering to ~7 km with prompt duck and covering within 2 seconds. One can think of this as going from a scenario where before the majority of people caught in the open, who just stood there staring at the fireball out to a radius of 11 km would probably die from lethal 3rd-degree burns on their unclothed skin, to a scenario where instead the vast majority of people who 'duck and cover' from 7 km out to 11 km would remain alive, with generally non life-threatening 1st-degree burns and 2nd-degree burns over their exposed skin, with the burn severity naturally depending on their range from the explosion. Finally, all the lethal ranges given in the referenced graphs, and when discussing the range of effects of nuclear explosions