OSHA standard  1910.157

1910.157(c)(1)

The employer shall provide portable fire extinguishers and shall mount, locate and identify them so that they are readily accessible to employees without subjecting the employees to possible injury.

NFPA 10

Extinguishers with a gross weight not exceeding 40 pounds should be installed so that the top of the extinguisher is not more than 5 feet above the floor.

Extinguishers with a gross weight greater than 40 pounds, except wheeled types, should be installed so that the top of the extinguisher is not more than 3 feet above the floor.

In no case can the clearance between the bottom of the extinguisher and the floor be less than 4 inches.

"shall be....readily accessible and immediately available in the event of fire." And also that "Fire extinguishers shall not be obstructed or obscured from view."

We mount the extinguisher outside the storage area and near the doors inside the lab so to maintain an 18 inch clearance to either side and a 36 inch clearance in front of the extinguisher. We use a standard sign the has an arrow that points to the extinguisher from a high 6 to 7 feet from the floor.

Jeff