Occupant-load thresholds: 50 and 300

One-line orientation

Two occupant counts are useful first checks. A room or space at 50 or more occupants commonly needs a second exit; a Group A occupant load of 300 or more triggers manual fire-alarm review. Area-of-refuge and backup-power rules use different triggers.

Key points

• ~50 occupants (50 or more) in a room/space → a second means of egress. One exit is no longer enough; the space needs two separate, remote exits.
• 300 or more occupants in Group A → manual fire alarm system review. Areas of refuge / safe areas and backup (emergency/standby) power are separate building-wide life-safety checks with their own triggers.
• Scope is the whole point: the 50 number is about one room/space; the 300 alarm cue is occupancy/building-level and, in the model code, tied to Group A. Same word (“occupants”), different unit of measure and different code section.
• These are screening triggers, not the only drivers — actual exit count, alarm requirements, and accessibility also depend on occupancy group, sprinklers, and area. Treat 50 and 300 as the fast first check.

Occupant load: 50 is a room; 300 is a Group A alarm cue

Same axis, different scope: 50 checks room egress; 300 checks the Group A building alarm.

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Key

• blue arrow = requirement keyed to this occupant count

Do not make 300 a bundle—areas of refuge and backup power have their own triggers.

Screening numbers—occupancy group, sprinklers, area, and the cited code provisions still govern the final requirement.

Confusions / comparison

Threshold (occupant load)	What it triggers	Code basis (per card)	Keyed to occupancy group?
50 or more in a room/space	A second means of egress — two separate, remote exits	IBC 2021 §1006.2 / Table 1006.2.1	Yes — one-exit cap is 49 for A/B/E/F/M/U but lower elsewhere (S = 29, I/R = 10, H-1–H-3 = 3)
300 or more (fire-alarm leg)	Central / manual fire alarm system	IBC 2021 §907.2.1	Yes — the literal 300 trigger applies to Group A
Large crowd (refuge leg)	Areas of refuge / safe areas	IBC 2021 §1009	No — tied to the accessible means of egress, not a 300 count; waived at sprinklered exit stairways
Large crowd (power leg)	Backup / emergency power	IBC 2021 §2702	No — system-driven (e.g. high-rise voice alarm), not an occupant count

Related

→ Exit stairs (this topic): the second exit is usually a second protected stair · Egress doors (this topic): the ~50 count also drives door swing direction · Area of refuge & standpipes (this topic): accessible-means-of-egress requirements that are separate from the 300 fire-alarm cue.