The moderator sphere1 is a passive dose equivalent meter for area monitoring of natural radiation background. It measures the neutron component of the natural annual background radiation of about 30 µSv. The monitoring period is at least 3 months. The passive neutron dose equivalent meter consists of a moderator polyethylene sphere of 300 mm diameter and a detector holder placed at a central position in the sphere. An Albedo dosemeter case with inserted TLD card is placed inside the detector holder for measurement. The user must specify the types of TLD card and Albedo dosemeter case. In addition to the standard version of the moderator sphere, a waterproof version is available for use in the open air. A special support made of aluminum is used to set up the moderator sphere free in air at a certain distance from backscatter material.