The safety briefing says "pull the mask towards you to start the flow of oxygen...". But how hard? A gentle pull or a hard tug? And can you tell straightaway when it starts? Has anyone on here had to do it?
On Iberia the Spanish language briefing uses the phrase "tirar fuertamente" which translates as "pull strongly" (firmly). The English version, IIRC, just says "pull". I believe there is a secondary wire/cord to prevent the oxygen supply tube being ruptured if too much force is used.