referring to the drawings , in fig1 the manikin 10 is made in size and configuration to replicate a typical man . the manikin is 1 . 7 meters in height and has an outer surface area of approximately 1 . 5 meters . the outer surface , or skin , has a soft feel and the body is flexible . the manikin has a perforated rigid plastic main frame 11 forming a trunk and head . the main frame 11 is covered by a breathable sealed skin 12 , that also forms arms 13 and legs 14 , which in use is filled with water . the manikin is shown in fig2 with a piece of skin ‘ torn away ’ to show part of the main frame 11 . the skin 12 is made of three layers , an outer layer of nylon , an inner layer of knitted fabric and a central layer of microporous polytetrafluoroethylene . suitable materials are already known and used for specialist sports clothing , such materials are available and sold as goretex ( trade mark ) material . a water heater 15 is inside the frame 11 , approximately where a human heart would be situated , and is connected to a supply pipe 16 . the pipe 16 provides a hanging support for the manikin . water passages inside the manikin are provided by a network of pipes 17 that lead from the heater 15 to extremities of the arms and legs . a pump 18 is used to pump water along the pipes 17 to provide a flow of water ( see arrows in fig1 ) around the inside of the manikin to simulate a natural blood flow of a human body . a topping - up gauge 19 is connected by a manually operable valve 20 to allow the manikin to be re - filled to a top up line with measured quantities of water , as required from time to time . this enables the amount of water used to readily determined after each testing period . when the manikin is supported by the pipe 16 , as described above , the arms and legs are generally free to swing backwards and forwards . swivellable joints 21 and 22 allow suitable relative movement between the pipes 17 . thus for simulating walking suitable mechanical ‘ pushers ’ ( not shown ) are positioned to pull and push the arms and legs , as required . in use , the manikin &# 39 ; s core temperature is controlled to be 37 ° c . normally the manikin is suspended inside a box frame , that may have outer walls to form a cabinet surrounding the manikin . the manikin can produce gaseons ‘ perspiration ’ to simulate human sweating which will vary according to the amount and type of clothing that is worn . in fig3 the manikin 10 is provided with a number of sensors ( known per se ) for supplying a computer 23 with information for determining operating conditions during testing . the computer is programmed to control a power supply to the heater 15 , while responding to a temperature sensor 24 inside the manikin , to maintain water temperature inside the manikin at 37 ° c . ; typically the normal body temperature of a human body . in use , the manikin produces heavy gaseous ‘ perspiration ’. the insensible perspiration of a human body is around 30 g / h , and when sweating can reach 1000 g / h . the perspiration of the manikin varies with the amount and type of clothing worn and can operate over a range of normal human perspiration . it is possible , by providing additional separately controllable pumps or adjustable - valves ( not shown ) for the pipes 17 , to vary the skin temperature distribution at the surface of the skin 12 where required . as the manikin is supported by the pipe 16 and hangs below the pipe , clothing can be easily put on and taken off the manikin . as already mentioned , the limbs of the manikin can by arranged to be mechanically moved to simulate walking . the computer is programmed to simultaneously determine clo ( thermal resistance ) and im ( permeability index ): clo = k · δ   t w   t where k is a constant of proportionality , δt is the temperature difference between the skin and surrounding environment , and w t is the dry heat loss . w t is the dry heat loss calculated from the total heat loss minus the heat loss due to perspiration . the im value is determined by the following equation : w = k clo  ( δ   t + i m · s · δ   p ) where c is a constant and equals 22 ° c ./ mmhg , δp is the vapour pressure difference between the skin at its temperature and the environment , and w is the total heat loss . the quantity of water that evaporates during each testing cycles , as explained above , is determined by ‘ topping up ’ the water inside the manikin using the topping up gauge 19 after each testing cycle . the table below shows typical test results for the described manikin : where t e is the mean “ skin ” temperature , t e the mean ambient temperature , hs the mean “ skin ” humidity , he the mean ambient humidity , w the total heat loss , q the total water loss due to perspiration , clo dv the standard deviation of clo value , im dv the standard deviation of im value .