They work with lists of people that they are supplied with, but they target the elderly and non residents because in their opinion they are easier to deceive.
After a thorough review of the gas appliances and connections, the scammer tells his victim that the facility is in poor condition and should be changed or it will be cut off.
The inspector makes false promises to expedite the process in exchange for a small gratuity or sometimes charging cash it costs to repair.
Most of the companies they work for these people are legal.
They may change elements... or sell other elements that are not mandatory. The more they charge the more they gain.
Do no open... even if they have the accreditation of gas inspector, unless you have arranged the visit previously.
If they contact you saying they will send someone to your house for a review, you must refuse. It is always the customer who calls the company.
Check your gas contract and check the dates of review (every 5 years). Failure to do so only involves a risk to you and problems with home insurance if an accident occurs.
If you decide to do a review, see the person who provides gas cylinders. He will provide phone numbers of official business.
The tube must be changed when it expires and the regulator when it stops working.