It is essential that engineers have carried out the correct gas courses before working on certain equipment, according to the Health and Safety Executive (HSE).
The industry body commented after a worker from Tywyn was fined £38,000 - as well as court costs of £15,711 - for breaching health and safety regulations by carrying out work on several items of gas machinery.
HSE inspector Gary Martin highlighted how it is essential that engineers have taken the right gas courses before going through with procedures such as this.
He remarked: "Fitters who try to work beyond their assessed competence are not only breaking the law but could also cost lives."
The defendant, Chris Bradshaw, potentially endangered people's lives through work he carried out on a person's house, with high levels of carbon monoxide gas recorded at the property.
Last week, the HSE called for people to check an engineer's Gas Safe ID card when they come round to install or maintain any equipment of this type.
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