ISO14644 does not specify numbers of probes, etc. It does emphasise minimum distances from walls, etc. The Area square root calculation is an air quality monitoring standard and should not be applied to this kind of study. You need to look at the room in a logical way, understand the air distribution throughout the room and consider the following as a minimum:
- Personnel movements
- Area size (cubicle vs warehouse)
- Heat stratification (warmer air rises, therefore air tends to be warmer at ceilings than at ground level in areas with fairly low change rates)
- Heat generating sources at working level (Human body temp, machine heat exhaust, etc)
- Room shape (regular 4-sided square/rectangular shape, irregular polygonal areas with dead space)
- Obstructions (machine installations, racking, etc)
- Air change rates. Warehouses with 5 air changes equilibrate more slowly than cubicles with 30 air changes.
Once these factors have been evaluated, you can decide on a mapping strategy. Minimum for cubicles would be 4 sensors in each corner at high and low level, usually about 30 cm away from the nearest wall, with 1 sensor in the middle at working height. For larger spaces, use 15 - 30 sensors, spaced at regular intervals at low-level, working level and high level to account for the factors mentioned above.
Hope this helps