Carbolite CDF 15/1b - Manual (Page 5)

CDF
MF56 – 1.03
5
the electric potential inside the chamber can be at any value between zero and the supply voltage.
Unearthed probes can cause serious electric shock.
3.4 Atmospheres
Chamber furnaces are not gas tight, so it should be understood that gas usage may be high, and that
the chamber is likely always to contain some air. Residual oxygen levels of 1% are to be expected.
In practice inert or oxidising gases may be used, but not combustible or toxic gases.