Haze and Fog Machine Output for a Venue

A hazed room is a steady state, not a fill: the machine adds haze continuously while the ventilation removes it continuously, and the density settles where the two rates match. That makes required output proportional to the PRODUCT of volume and air-change rate. Double the room and you need twice the machine; leave the room the same size and double the air handlers and you also need twice the machine. Crews consistently size on volume alone and are then surprised the look will not hold once the HVAC comes on for the audience. The time constant is the other half. At 4 air changes per hour a room reaches 63% of its final density in 15 minutes and 90% in about 35, so a haze cue called two minutes before the top of the show does nothing and the machine has to have been running through the pre-show; at 1 air change per hour the same room takes over two hours to settle, which is why a tight room hazes beautifully and then will not clear for the next act. A 200,000 cubic ft hall at 4 air changes moves 13,333 cfm and, scaled from a machine that holds a good haze in a 100,000 cubic ft room at 2 air changes on one quart per hour, needs four quarts an hour -- four times the fluid for a room only twice as large, because the air handlers did half the damage. If the house will run at 2 air changes during the show the requirement halves and the pre-show fill takes twice as long, and that negotiation with the building engineer is worth more than a second machine. A scaling estimate; the machine manufacturer's rated output, the fluid's safety data sheet, and the venue's smoke-detection and fire-authority requirements govern.

ventilation_cfm = volume_cf x ach / 60; scaling_factor = (volume_cf x ach) / (ref_volume_cf x ref_ach); required_output = ref_output x scaling_factor; time_constant_hr = 1 / ach; time_to_90_hr = ln(10) / ach.

Haze density as the steady state between machine output and ventilation removal, scaled on the product of volume and air-change rate, with the first-order fill time constant 1/ACH, by name; public mass-balance physics. The machine manufacturer's rated output, the fluid's safety data sheet, and the venue's smoke-detection and fire-authority requirements govern.

The steady-state mass balance and its exponential approach are public physics. The venue volume, air-change rate, and the reference machine's performance are the user's own values.

Estimate. AHJ and licensed professional govern.

Field names used by the API: volume_cf, ach, ref_volume_cf, ref_ach, ref_output, ventilation_cfm, scaling_factor, required_output, time_constant_hr, time_to_90_hr

• Steady state required output scales on the PRODUCT of volume and air-change rate, not on volume alonemass balance
• Fill time first-order approach: 63% of steady state at 1/ACH hours, 90% at ln(10)/ACHfirst-order system response
• Governing authority the machine's rated output, the fluid's safety data sheet, and the venue's smoke-detection and fire-authority requirements governvenue fire authority