Borehole temperature monitoring

A method of monitoring the temperature in a borehole (42) in which a detonator (40) is deployed in order to determine the existence of a hot hole condition, wherein the method includes the steps, prior to such deployment, under controlled temperature conditions, of using an oscillator (16) which functions at frequency which is temperature-dependent to determine a first measurement which is based on the frequency of oscillation (f1;

• F1) of the oscillator at a first temperature (T1) and a second measurement which is based on the frequency of oscillation (f2;
• F2) of the oscillator at a second temperature (T2), using said first and second frequency measurements and said first and second temperature measurements to establish a frequency versus temperature relationship for the oscillator and storing said relationship in a memory unit (14) in the detonator (40), deploying the detonator in the borehole (42), placing an emulsion explosive (52) into the borehole surrounding the detonator, subsequent to such placement, obtaining a third measure of the frequency of oscillation (f3;
• F3) of the oscillator and using said frequency versus temperature relationship to determine the temperature of the oscillator (“the third temperature”) (T3) and using the third temperature to assess whether the temperature in the borehole is indicative of a hot-hole condition.