must be observed and the cable must be supported at regular intervals. The magnesium oxide insulation is hygroscopic so MICC cable must be protected from moisture until it has been terminated. Termination requires stripping back the copper cladding and attaching a compression gland fitting. Individual conductors are insulated with plastic sleeves. A sealing tape, insulating putty or an epoxy resin is then poured into the compression gland fitting to provide a watertight seal. If a termination is faulty due to workmanship or damage then the magnesium oxide will absorb moisture and lose its insulating properties. Depending on the size and number of conductors, a single termination can take between 1 and 2 hours of labour (an electrician should be able to make a termination in 10 to 15 minutes on up to 4 core smaller sizes). Installation of a three-conductor MI cable (size No. 10 AWG — about 5 square mm) takes about 65% more time than installation of a PVC-sheathed armoured cable of the same conductor size. Installation of MICC is therefore a costly task. Certain PTFE, silicone or other polymer-insulated cables have been substituted in applications which require similar properties in terms of flame spread, which use less labour to terminate. MICC is still used in applications which are particularly suited to its combination of properties. Voltage rating: MI cable is only manufactured with ratings up to 1000 volts. Moisture absorption: The magnesium oxide insulation has a high affinity for moisture. Moisture introduced into the cable can cause electrical leakage from the internal conductors to the metal sheath. Moisture absorbed at a cut end of the cable may be driven off by heating the cable. Corrosion: The copper sheath material is resistant to most chemicals but can be severely damaged by ammonia-bearing compounds and urine. A pinhole in the copper sheathing will allow moisture into the insulation, and eventual failure of the circuit. A PVC over jacket or sheaths of other metals may be required where such chemical damage is expected. When MI cable is embedded in concrete as snow melting cable it is subject to physical damage by concrete workers working the concrete into the pour. If the 3-5mil coating is damaged pin holes in the copper jacket develop causing premature failure of the snow melting system. Repair: If the MI cable jacket has been damaged the magnesium oxide will wick moisture into the cable and it