Download Fog and Smoke Effects on Stage

Fog and Smoke Effects on Stage
ABTT Code of Practice CP015 July 2014
USE OF STAGE FOG EFFECTS
How safe are Fog and Smoke Effects in a Theatre?
Fog effects are often used in theatre to create magical effects. Typically they are of two
types, low-lying and atmospheric. The low lying type is the fog that performers walk or
dance through to give an above the clouds effect, and atmospheric fog is swirling mists
for outdoor effects.
Fog is very fine particles of fluid whilst smoke is solid particles such as given off by
burning wood and pyrotechnic effects. Fog effects are created by special purpose
machines and use either water (such as the “Dry Ice” effect) or chemicals such as Di and
Trihydiric Alcohols or less often Glycol. None of these chemicals are poisonous to
humans except in vast quantities and may be ingested without ill effects. However, there
is a tiny minority of the population who may suffer respiratory discomfort when exposed
to these chemicals in very high quantities. The work in determining these levels was
conducted by the Mount Sinai Hospital in Manhattan in 2002 in a study funded by the
then ESTA (now PLASA) and endorsed by American Equity. From these and other tests,
Occupational Exposure Limits for the type of chemicals found in fog effects were laid
down in the United States. There are no such limits in the United Kingdom or in Europe,
although tests have been conducted in the UK by the Health and Safety Laboratory to
establish that the fog fluids contain the mixtures as labeled.
PLASA, through their Fog and Smoke Working Group have over the past 20 years
carried out significant work to investigate and educate about the safe use of fog. Their
work includes commissioning independent reports and collation of publications relating
to fog safety, albeit with a US and NIOSH bias.
In March 2014 the ABTT held a workshop meeting in the Playhouse Theatre in London
to demonstrate the testing of theatrical fog concentrations using a calibrated aerosol
monitor in order to observe the visible amount of fog required to reach the maximum
levels recommended in PLASA's "Introduction to modern atmospheric effects".
Hire stock sample fog machines manufactured by Look solutions were utilized for the
testing. These included two types of machine and two types of fluid (Aqueous Solutions
of Di- And Trihydric Alcohols )and were typical of those currently in common use in the
West End and many other locations.
At the meeting, two methods for evaluating concentration of fog output from the fog
machines were discussed and demonstrated.
1. Direct Measurement
A specialist aerosol monitor was used to measure the instantaneous and time averaged
concentration of fog in each effect. The test meter used photometry to report the
concentration of particles in the air by measuring the amount of light refracted by
particles passing in front of its sensor.
The meter readings demonstrated that in typical use, concentration of fog particles
rapidly dropped below recommended maximum levels, though peak limits may be
exceeded close to the output from the fog machines when emitting.
As a very rough rule of thumb, if an outstretched hand is obscured at arm’s length by
theatrical fog, the recommended maximum peak aerosol level of 40 mg/m3 has been
reached.
2. Using time / distance exposure tables
If a meter is not available concentration may be estimated using time / distance exposure
tables provided by manufacturers.
These tables provide an alternate simple method by having recorded the concentration of
atmospheric fog against time and distance following discharge from a particular fog
machine on a typical stage. Although this does not take into account a specific
production's use, and air conditions, it allows a rule of thumb approach without the need
for specialist test equipment. As an example, the table for a Rosco 1600 fog machine
using Stage & Studio Fluid, reports that a performer may be within 2m of the front of the
machine for 80seconds following operation for 10seconds on medium setting and
exposure will not exceed the recommended peak levels.
FAQs
How do I find out about best practice for safe use fog effects?
The “Introduction to modern atmospheric effects” published by PLASA, and available
from PLASA’s website provides an overview of fog effects, associated risks and
managing exposure.
Are there recommended exposure limits for atmospheric fog?
PLASA’s ANSI E1.5 includes recommended limits for exposure based on the chemicals
used in fog fluids. This gives 10 mg/m3 (Time waited average (TWA)) long term
exposure for mixture of water and dihydric and trihydric alcohols.
40 mg/m3 (Peak) for mixture of water and dihydric and trihydric alcohols.
50mg/m3 (Peak) for mixture of water and trihydric alcohol (glycerine)
In UK and US standards are also available for mineral oils recommending limits of :
5mg/m3 (TWA) and 25mg/m3 (Peak) for Mineral Oil
I would like to measure fog levels in my show to confirm that they do not exceed
peak levels. What do I need?
An aerosol meter may be hired for a cost of around £250 per day. The ABTT is able to
assist with locating a suitable meter.
The manufacturer of the fog machine should be contacted to determine appropriate
calibration factors for use with the meter.
Analysis of fog concentration against recommended standards
ANSI E1.5 sets out recommended peak exposure limits for the chemicals used in fog
fluids. These limits have been endorsed by American Actor's equity.
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ANSI E1.5 - Theatrical Fog Made With Aqueous Solutions of Di- And Trihydric
Alcohols
ANSI E1.14 - Recommendations for Inclusions in Fog Equipment Manuals
ANSI E1.23 - Design and Execution of Theatrical Fog Effects
ANSI E1.29 - Product Safety Standard for Theatrical Fog Generators that Create
Aerosols of Water, Aqueous Solutions of Glycol or Glycerin, or Aerosols of
Highly Refined Alkane Mineral Oil
© Association of British Theatre Technicians 2014