ROI and Fallow Time Calculator Fallow time Calculator To calculate fallow time using the CDC’s formula, you require the room volume, air flow and a multiplier called K-factor. k-Factor is the multiplier that represents the efficiency of air exchange for when calculating fallow time. 0: Perfect elimination of generated aerosols from their source (Viral-Vac™ DentalVac) 0.25: Most aerosols removed from their source (Viral-Vac™ DentalVac with safety margin) 1: A perfect exchange. i.e. air entering one end of a tube and then exiting out the other. 3: CDC uses 3 to represent isolation rooms in hospitals. 4-6: Floor standing HEPA filters with high air flow in the centre of the room. (Use 4 for the Vortex) 7-9: HEPA filters placed in corners depending on CFM and the ability to push air to the opposite corners. 10: Wall mounted HEPA filters generally do not have enough air flow to be effective at remote corners of a room. The RCDSO uses a k-factor value of 1 for calculating fallow time. The CDC does not recommend this. CDC does recommend negative pressure isolation rooms with 12 air exchanges/hour (ACH). k-Factor: —————————————————————————— Please enter the dimensions of your room and the number air exchanges (ACH) at your office. Room Width (ft) ( m) Room Length (ft) ( m) Room Height (ft) ( m) Building HVAC Air Exchanges (ACH) (enter 0 if you are not sure) Room Volume: ft3 ( m3) —————————————————————————— Fallow Time (pre COVID): 0 minutes Fallow Time (COVID, no changes to office): minutes (as per RCDSO assume 180 minutes if no knowledge of HVAC system) Fallow Time (with Viral-Vac™ DentalVac): minutes (ACH=) Fallow Time (with Viral-Vac™ Vortex): minutes (ACH=) Compare to your system. Please select the airflow of your filter and its efficiency (k-factor) CFM of comparison filter ( l/min) k-factor of comparison filter and room configuration: Fallow Time of comparison filter: minutes (ACH=) —————————————————————————— Revenue (pre COVID): $ per day Revenue (COVID, no changes to office): $ per day Revenue Potential (with Viral-Vac™ DentalVac): $ per day Revenue Potentail (with Viral-Vac™ Vortex): $ per day —————————————————————————— ROI of Viral-Vac™ DentalVac: (days) ROI of Viral-Vac™ Vortex: (days) Ave Work Hours Per Day Ave Time With Patient (min) Price Of 1 Unit of Scaling $ Assumes only 1 operatory. Adapted from: Centers for Disease Control and Prevent, Guidelines for Environmental Infection Control in Health-Care Facilities (2003): Table B.1. Air changes/hour (ACH) and time required for airborne-contaminant removal by efficiency. Available at: https://www.cdc.gov/infectioncontrol/guidelines/environmental/appendix/air.html#tableb1. This page assumes using True HEPA filtration units that are 99.97% efficient at removing particles down to 0.3 microns
