Shares in ALS, the Brisbane-based testing and certification company, fell almost 4 per cent on Tuesday after its CEO, Raj Naran, abruptly quit citing family reasons weeks before the end of the financial year.

Mr Naran, a former conscript in the Rhodesian Bush War in the 1970s who later studied chemistry in the US and ultimately ran Brisbane-based ALS for six years, resigned effective immediately, the company said on Tuesday.