It is effective but it is in fact, for some people exert very strong pressure. It does not necessarily have to be a senior or have "lost the strength of his hands," everyone just has not the same force.
I have at times failed to burn my hand. It should not hesitate to approach his inch from the end of the button, and press it repeatedly by lighting a small gas.
* Update * After a month of use, daily and not intenive, it no longer works.