Fill this poster in for the room and hang it by the laboratory door, where anyone scheduling the room can see the number.
What is on the poster
The fire and building codes set the number. Everyone in the room counts, adults included.
Fill it in for this room
| Step | This lab |
|---|---|
| Net floor area, in square feet: the occupied area, benches and fixed cabinets taken off | __________ sq ft |
| Divide by 50 square feet per person (labs and shops) | = ________ people |
| Take off the teacher, every aide and any visitor | = ________ students |
| NSTA: no more than 24 students in a science class | Use the lower number |
Worked example
| A lab 30 feet by 30 feet | Result |
|---|---|
| 900 sq ft ÷ 50 sq ft per person | 18 people |
| 18 people less the teacher | 17 students |
| With one aide in the room | 16 students |
| A class of 24 plus the teacher needs 25 × 50 | 1,250 sq ft |
The occupant load is a ceiling, not a target. A room at its limit has no space for an extra student, an aide or a visitor.
The poster draws a 30 by 30 foot lab holding 18 people, one of them the teacher: 17 students, not 24.
Built to the Science Safety Teaching Standard
This poster carries the SSTS mark. Like every Science Safety course, it is built to the Science Safety Teaching Standard (SSTS): every rule on it is taken from the body that governs it, at its current edition, and the source is printed on the poster, so you can check it yourself.
Stay current
When you get this poster, it is saved to your Science Safety account. If we revise the poster, or the Class Size and Safety module it comes from changes, we will email you, and the latest version will be waiting under Downloads in your account. Every revision carries its revision number and date at the bottom of the poster, so you can tell at a glance whether the copy on your wall is current.
Printing and hanging
- One-page PDF, US letter (8.5 by 11 inches).
- White background, so it prints clearly on any office or classroom printer without using much ink.
- Fill it in and hang it by the laboratory door.
- The QR code in the blue title band opens this page, so anyone can get their own copy.
- The QR code at the bottom opens the Class Size and Safety module.
Learn more
The Class Size and Safety module teaches the full topic this poster comes from.
Sources:
- International Building Code, Section 202, Floor Area, Net – International Code Council, via UpCodes (reviewed October 2, 2026)
- IR A-26, Occupant Load Factors for School Buildings – California Division of the State Architect (reviewed October 2, 2026)
- Liability of Science Educators for Laboratory Safety (2024) – National Science Teaching Association (reviewed October 2, 2026)
Poster SSP-0056, Rev. 1, October 2026.
