Neither OSHA or NFPA provide a specific distance that must be left clear around a fire extinguisher. At 1910.157(c)(1) OSHA states only that you shall “mount, locate and identify (fire extinguishers) so that they are readily accessible to employees without subjecting the employees to possible injury.” NFPA 10 Standard for Portable Fire Extinguishers requires at 1-6.3 that fire extinguishers are placed so that they are clearly visible and can be easily reached at once. At 1-6.6, it prohibits fire extinguishers from being blocked.
If an employer can quickly go to the fire extinguisher and is able to easily reach the extinguisher, OSHA should be satisfied. Most employers keep the floor beneath the fire extinguisher clear, and will mark that area with tape or floor markings so that nothing is inadvertently placed there.