Allowance for my son

if he goes to your local community welfare officer he should be entitled to supplementary welfare allowance

Is he claiming Jobseeker's Allowance? This is means-tested and if he is living at home, parents' income will be taken into account when assessing him. It is unlikely the CWO will entertain a claim to supplementary welafare allowance unless he has lodged a claim with SW.

As welfarite said, it is a requirement for a person claiming SWA from the Community Welfare Officer that they apply for any other Social Welfare payment they may be entitled to. In your son's case, he must apply for Jobseeker's Allowance before being considered for SWA.

The means test which applies to Jobseeker's Allowance also applies to SWA (i.e. son assessed on parent's income if any).

He is not claiming anything. He only has 30 PRSI contributions from his Fas course. What does the means test consist of ?.

As Welfarite said, if your son is living at home, he will be means-tested on parental income (if any). When your son makes a claim, he will be asked to present wage slips or P60s from his working parent(s). If parents are on a Social Welfare payment themselves, then no means would be assessed.
Other items assessed for means are savings over 20k, or property in the claimant's own name which is not being used by the claimant.