Sabbatarians who refused to work Sundays were to be excluded from bunker control teams for responding to a nuclear attack on Northern Ireland, official archives showed.
Members of the key units were also selected on grounds of physical fitness and age, according to NIO files released from 1983.
The draft criteria were to be used in the selection of new members for four area control teams situated in the north, south, east and west.
The document added: "Claustrophobia is hardly an advantage either in a windowless bunker."
The paper from the Home Defence Planning Committee was released by the Public Records Office of Northern Ireland (PRONI).
It said: "We know that given the conditions of bunker life with its constraints and the nature of problems that will have to be faced post-attack, that all the team will be working under extreme pressure and the nominee will therefore have to be able to take and control stress, remaining efficient."
Up to 75 people were intended to form a team able to form within two days, with appropriate accommodation and communications.
The file disclosed that the need for the setting of criteria has been made apparent by the quality and enthusiasm of recent and/or existing team members.
It added: "It is apparent that a percentage of the existing team members lack enthusiasm and their efficiency obviously suffers."
Other proposed criteria included family commitments.
"A person with a large family would be undesirable as they may be more inclined to put family responsibilities first, making arrangements for their well-being.
"Therefore a person with a small family is a probable requirement and preferably children approaching adulthood and hopefully self-sufficiency."
The draft guidance also covered physical disabilities.
"Given the conditions within the bunker with all its constraints on both space and facilities and indeed the very nature of the work expected of team members, persons with any physical disability except those of a minor nature would be at a disadvantage."
It said an upper age limit of around 50 should be set for health reasons but acknowledged wide-ranging knowledge of an organisation was likely only after years of service. Those with specialised dietary requirements and those who required medical drugs would be undesirable.
The final criteria covered membership of outside groups.
"We should avoid nominees who hold sincere views of the nature of Lords' Day observance, Exclusive Brethren etc."