I serve on several different organizations. Usually, the members are not paid, but often their employers will support there activities. These committes are usually "steered" by one or more national/international associations in addition to the organization the administrates the documents and schedules the meetings. Because of the time required, the persons that are very active are usually strongly supported by their employers or independantly wealthy. - It is not cheap or easy to be actively involved.
Academic people may be supported by the school or programs, especially if research projects are required. Producer members are usually supported by their employers. Users (usually designers, specifiers and buyers, etc.) may be independent or supported by firms. Intersted parties may be "little old ladies" than can really thow in snag in process if they gang up at one time for their cause like the saefy and design of a pet access door that can effect the HVAC of a building.
Committe membership is usually open to all members of the group (ASTM, ACI, ASCE, etc.) establishing the standards/codes. Usually, the dues are minimal (as an example, ASTM is only $75/year with a free volume) and usually personal.
Getting to be a voting member may take time, presence, activity and persistance. Some groups require a "balanced" representation (user, producer and interested parties equally or something similar), so openings only occur when the number of voting members gets below a desired level AND there are applicants on the waiting list in a specific category. It took me over 10 years to be a voting member on one ASTM committee. Most votes are individual and not corporate and the number of voting members from one corporation/entity may be limited.
If you do not have any support, it can be costly, but it is educational and rewarding.
Often, there are annual or two times a year meetings that are usually at locations where the travel and lodging can be very pricey. Much of the work can be handled by E-mail, etc. Some groups do not requre actual attendance, missing meetings means missing much of the real meat and backgound on proposals. There are required minimal voting requirements, so lack of voting can terminate the voting status.
Most of the work on material and design stanards does not have real legal standing in codes until it is adopted by a code, code autority, specifying authority or a specifier. This activity for anyone that expects a quick solution or change in codes or standards.
Dick