Calibration Factors for Monitoring Theatrical Fog and Haze

The accurate monitoring of theatrical fog and haze is crucial for ensuring that exposure levels remain within safe limits, thereby protecting the health of performers, crew, and audiences. One of the key tools in this process is the use of aerosol monitors, which measure the concentration of particles in the air. However, to ensure that these measurements are accurate and reliable, it is essential to apply calibration factors specific to the type of fog or haze being used. This section explores the importance of calibration, the methods for determining calibration factors, and the practical application of these factors in monitoring fog and haze during theatrical productions.

The Importance of Calibration

Aerosol monitors, such as the Thermo Scientific PDR-1000AN, are widely used in the entertainment industry to measure the concentration of fog and haze particles in the air. These devices provide real-time data on particle density, which is critical for assessing whether the levels are within the safe exposure limits established by standards like ANSI E1.5-2009 (R2014). However, the accuracy of these readings can be influenced by several factors, including the specific characteristics of the fog or haze fluid, the particle size distribution, and the environmental conditions.

Calibration is the process of adjusting the monitor’s readings to account for these variables, ensuring that the data reflects the true concentration of particles in the air. Without proper calibration, the readings from aerosol monitors may be inaccurate, potentially leading to either an underestimation or overestimation of exposure levels. This can result in inadequate protection measures, putting individuals at risk, or unnecessary over-caution, which can disrupt the production process.

Determining Calibration Factors

Calibration factors are specific adjustments made to the readings of aerosol monitors to account for the unique properties of the fog or haze being measured. These factors are determined through a process that involves the following steps:

1. Characterizing the Fog or Haze Fluid:

• The first step in determining calibration factors is to characterize the fog or haze fluid used in the production. This includes analyzing the chemical composition, particle size distribution, and the fluid’s behavior under different environmental conditions. For example, glycol-based fluids may produce particles of a different size and density compared to mineral oil-based fluids, requiring different calibration adjustments (Ramboll, 2023).

1. Laboratory Testing:

• Once the fluid is characterized, laboratory testing is conducted to establish the relationship between the actual particle concentration in the air and the readings from the aerosol monitor. This involves generating fog or haze under controlled conditions and measuring the particle concentration using both the aerosol monitor and reference methods such as gravimetric sampling, where particles are collected on a filter and weighed (Ramboll, 2023).

1. Developing Calibration Curves:

• The data obtained from laboratory testing is used to create calibration curves, which plot the aerosol monitor readings against the actual particle concentrations. These curves allow for the calculation of calibration factors—specific numerical values that are applied to the monitor’s readings to adjust them to reflect the true particle concentration (Ramboll, 2023).

1. Field Validation:

• After developing the calibration factors in the laboratory, they must be validated in the field. This involves using the calibrated aerosol monitor in real-world production environments and comparing the readings to those obtained from reference methods. Field validation ensures that the calibration factors accurately account for the variables present in the actual production setting, such as differences in temperature, humidity, and air movement (Ramboll, 2023).

Practical Application of Calibration Factors

Once calibration factors are determined, they can be applied in the daily monitoring of fog and haze during theatrical productions. The practical application involves several key steps:

1. Regular Calibration Checks:

• Calibration factors should be regularly checked and updated as necessary, especially when there is a change in the fog or haze fluid, the aerosol monitor, or the environmental conditions. This ensures that the monitoring data remains accurate and reliable throughout the production (Ramboll, 2023).

1. Real-Time Monitoring:

• During rehearsals and performances, the calibrated aerosol monitor provides real-time data on particle concentrations. Technicians can use this information to make immediate adjustments to the use of fog or haze, such as reducing the output from the fog machine or increasing ventilation, to maintain safe exposure levels (Safety Bulletin #10, 2019).

1. Data Logging and Reporting:

• The data collected by the aerosol monitor should be logged and reviewed regularly to ensure that exposure levels are consistently within safe limits. This data can also be used for reporting purposes, providing documentation that the production is adhering to safety standards and protecting the health of all involved (ANSI E1.5-2009, 2014).

1. Training and Implementation:

• It is essential that all technicians and safety personnel involved in the production are trained in the use of calibrated aerosol monitors and understand how to apply the calibration factors. Proper training ensures that the monitoring process is implemented correctly and that any potential issues are identified and addressed promptly (Safety Bulletin #10 Addendum A, 2019).

Case Studies and Research Findings

Research and case studies have demonstrated the importance of using properly calibrated monitors in maintaining safe fog and haze levels during productions:

• Ramboll (2023): In their study on calibration factors, Ramboll emphasized the critical role that calibration plays in ensuring the accuracy of aerosol monitors. Their research highlighted how even small discrepancies in calibration could lead to significant differences in reported exposure levels, potentially compromising safety.
• Colden-Phylmar (2018): The Colden-Phylmar report for CSATF stressed the need for continuous monitoring and the application of calibration factors to ensure that theatrical fog and haze remain within safe exposure limits. The report also recommended regular re-calibration of monitors to account for changes in environmental conditions or fluid composition.

Conclusion

Accurate monitoring of theatrical fog and haze is essential for maintaining a safe production environment. Calibration factors play a crucial role in ensuring that the readings from aerosol monitors reflect the true concentration of particles in the air, allowing for effective risk management. By following the outlined procedures for determining and applying calibration factors, production teams can confidently use fog and haze effects without compromising the health and safety of performers, crew, and audiences.

References

• ANSI E1.5-2009 (R2014). (2014). Theatrical fog made with aqueous solutions of di- and trihydric alcohols. PLASA North America.
• Colden-Phylmar. (2018). Theatrical fog review final report for CSATF.
• Ramboll. (2023). Theatrical smoke, fog, and haze testing: Calibration factors.
• Safety Bulletin #10. (2019). Guidelines regarding the use of artificially created atmospheric fog and haze. Industry-Wide Labor-Management Safety Committee.
• Safety Bulletin #10 Addendum A. (2019). Atmospheric fog & haze – Technical awareness sheet. Industry-Wide Labor-Management Safety Committee.