Smoke Particle Size - why smaller is better!

Common to this range of smoke generators is our incorporation of precision, machined, specially treated steel heat exchanger blocks in which the smoke chemical is vaporised.

Conventional smoke generators normally use either cast or platen type aluminium heat exchangers, which whilst very cost effective to make, generally produce a smoke particle with a mass median diameter (mmd) of 1 - 10 microns.

This compares with a typical particle size of just 0.2 - 0.3 micron mmd for our smoke systems below, be they water or oil based.

The general benefits of producing such a consistent and clearly defined particle distribution are:

• the smaller the particle size of the smoke, (or more accurately fog) the smaller the amount of chemical is required within the atmosphere to achieve any given visibility. This can have a significant effect on running costs for heavy users of artificial smoke (fire brigades etc.)
  
• the less the amount of chemical in the atmosphere, the safer the smoke if measured in terms of relative Occupational Exposure Levels.
  
• the smaller the particle size of the smoke, the lower its settling velocity (the rate at which a particle will fall, due to gravity). A smoke particle of unit density, 0.2 micron in diameter, will fall at 8mm/hour, compared to a 2 micron particle, which falls at 468mm/hour. In essence this means that the smaller the particle of smoke you produce, the less chance there is that deposition of smoke particles will occur on surfaces.
  

Small particle size = no residue!

The terminal settling velocity of an aerosol or "artificial smoke" particle increases rapidly with particle size. The settling velocity is proportional to the square of the particle diameter, although sub micron particles, such as those produced by Pea Soup branded smoke systems require the use of slip correction factors.

Calculated for standard density spheres at 293 K [20° C] and 101 kPa (1 atm).
"Aerosol Technology", William C. Hinds, Wiley-Interscience, 1999

	Rocket Hand Portable Smoke Machine - hand-portable unit. Can deliver quick dispersing smoke (PS21) or long lasting (PS23). Off-power facility. 240/110v.
	Dragon 2.2kW High Output Smoke Generator - continuous high output 2.2kW machine with a choice of fluids available for either quick dispersing smoke or persistent. 240/110v.
	Oil Based Smoke Generator - oil-based smoke machines with continuous highly controllable output. The generated smoke can withstand high temperatures, is very persistent and has a very small particle size (no residue) and can easily be ducted. 240/110v.

The Oil Based Smoke Generator in operation