Measurement of dose rate due to outdoor radiation in Rasht city by using gas dosimeter

External human radiation due to radiation from natural resources is much more than artificial sources. In this study, the amount of outdoor background radiation was measured in different parts of Rasht city and the dose rate was calculated.RDS-110 was used to measure background radiation in this cross-sectional study.To measure background radiation at the same height, a metal base with a height of one meter was used and the device was placed on it.Dose rate equivalent to background radiation for outdoor space was measured in nine areas (north, south, east, west, center, northwest, northeast, southwest and southeast) and for each point twelve stages were measured at 5 minutes intervals.The average dose rate equivalent to background radiation and its standard deviation in the outdoor is  79/88±5/74nSv/h which is 34% higher than the global average of the equivalent dose rate.Also, the annual effective outdoor dose rate in Rasht city is 0/098±0/007mSv/y, which shows a higher amount compared to the global average of effective outdoor dose rate.