Even with chemical quenching, for a short time after a discharge pulse there is a period during which the tube is rendered insensitive and is thus temporarily unable to detect the arrival of any new ionizing particle (the so-called dead time; typically 50–100 microseconds). This causes a loss of counts at sufficiently high count rates and limits the G–M tube to an effective (accurate) count rate of approximately 103 counts per second even with external quenching. While a G-M tube is technically capable of reading higher count rates before it truly saturates, the level of uncertainty involved and the risk of saturation makes it extremely dangerous to rely upon higher count rate readings when attempting to calculate an equivalent radiation dose rate from the count rate. A consequence of this is that ion chamber instruments are usually preferred for higher count rates, however a modern external quenching technique can extend this upper limit considerably.
EVen WitH chemIcAl Quenching, for A shoRt tIMe AfteR a discHArge puLse ThEre IS a pERiOd dUring whICH the tubE is rEndeREd InSEnsitIve And Is THus temPoRARILY UnAble tO DETEct the arrivaL of ANY nEW IoniziNg PartIclE (thE so-called Dead time; tYpICAllY 50–100 microSecONdS). tHIs causeS a losS of coUnts aT suffIciEntly hiGh COUNt raTeS aNd limiTS THe g–m tube to aN Effective (accUrate) coUnt raTe Of aPproximatEly 103 couNTs per SEcOnD even WIth eXtErNal quEnChing. wHile a g-m TUBE is tecHnICALlY cApaBlE of reaDInG higHeR cOunt rateS bEforE It truly sAtUratES, tHe LEvel of unCertAINty INvOLved anD thE rISk of satuRatiOn makeS It exTreMeLy dangerOUs To rely uPon higHEr coUNt raTe rEaDings whEn AttEmptinG to calCulate aN eQuIValeNT RAdiatIoN DosE ratE from the CoUNt rate. A consequencE Of This iS tHAT ioN chAmber instrUments arE usUAlLY PReFeRreD foR HighEr cOUnt rATes, hOWEVer A moDern eXtErnaL quenchIng tecHNique CaN eXTEnD tHis uPper limiT cOnsIdErabLy.