PART A: COMPUTE THE TIME OF ENTRY INTO A FALLOUT AREA
To determine the time of entry into a fallout area using the total dose (fallout) nomogram (Figure 3-1),
you must know:
The total dose.
The dose rate at H + 1 hour.
The time of stay.
How to extract the time of entry from the nomogram.
Determine the Total Dose.
To use the total dose (fallout) nomogram (Figure 3-1), the total outside dose must be determined. This
is based on the operation exposure guidance (OEG) established by the commander. For unprotected
personnel, the OEG will be the total dose used on the nomogram. If the personnel are protected by some
type of shielding, the total outside dose may be much greater than the OEG. As an example, if the
personnel were operating inside M113 Armored Personnel Carriers (transmission factor of 0.3), the total
outside dose would be 83.3 cGy at the time the personnel had received only 25 cGy of radiation. This is
determined by dividing the inside dose by the transmission factor. In this case, 83.3 cGy would be the
value used on the total dose scale of the nomogram.
Determine the Dose Rate at H + 1.
The H + 1 hour dose rate which is used on the nomogram can be estimated by observing the area to be
situation map. The dose rate, when applied to the total dose (fallout) nomogram, must ALWAYS be
referenced to H + 1.
Determine the Time of Stay.
The time of stay in the fallout area will normally be dictated by the mission. In other words, how long
will it take to accomplish the mission once the personnel are in the fallout area?
Determine the Time of Entry From the Nomogram.
When the total dose, dose rate, and time of stay are known, the time of entry into a fallout area can be
determined from the total dose (fallout) nomogram using the following procedures.
Locate the total dose value on the total dose scale. Place the end of a hairline on this
mark. Hold it in place with a pin or sharp pencil.