Theatrical Fog and Known Health Effects
16/08/2022, updated on 06/12/2025
Modern stage productions can create truly spectacular visual effects ✨💥🔥💨 The kind that make audiences go “WOOOOOOOOW! 😮”
But as impressive as these effects are, many singers notice that they can also create unexpected challenges for the voice. As your voice teacher, I believe it’s essential that you understand the different types of stage effects, how they may impact your vocal health, and which safer alternatives you can request when needed. I strongly encourage you to communicate with your show’s designers so you can find a healthy balance between visual impact and optimal vocal performance. Your voice is irreplaceable, you hàve to protect it.
During one of Pauline Slangen’s performances in The Masked Singer Belgium 2025 (VTM), fireworks created a heavy cloud of smoke. Suddenly she couldn’t breathe. Her throat tightened, the smell was overwhelming, and her voice nearly gave out… but she had to keep going. She panicked. The reaction of one of the technicians backstage left me baffled…
Click here to read her full story in my newsletter.
Some of my clients share that effects designers are sometimes dismissive of their concerns. I’m convinced that most of the time, this isn’t intentional. Most designers simply never receive training about (vocal) health and are unaware of the risks. Sharing this blog post with them may help bridge that gap.
But first:
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Susanne Vahle - Vocational singer
Manon Campens - Singer
Bec Tilley, Voice Coach & Singer
Haike D'haese - Singer & Actress
I highly recommend Sarah if you are looking for a voice specialist!
Gwendy - Vocational singer
Dr. Tracy Smith Bessette - Singer, Voice Instructor, Early Music Coach & Course Lecturer
Breg Horemans - Vocational singer
Susanne Vahle - Vocational singer
Ariane De Dom, Avocational singer
Diane Speirs - Singer & Voice Teacher
I leave our lessons feeling inspired and with new tools to use with my voice students. I particularly love that I now have language to identify and describe with more specificity the different kinds of sounds that live in pop/rock styles. Working with Sarah has made me a better teacher for my students!
M.J. Johnson, Singing Teacher and Vocal Coach
Kim, Avocational Singer
You learn to look for a solution and deal with your struggles yourself. It's not pre-made shit, it's to the point.
Esther De Bièvre - Recovery therapist
Pieter Van Hecke, Vocational singer
Nele - Singer & Youth Library Worker
Nele Willekens - Library youth worker
Bec Tilley, Voice Coach & Singer
Stella Handley, Avocational singer
Janet Wilson - Vocational singer
Esther De Bièvre - Recovery therapist
Kenneth Ottoy, Singer of Plagiaat & Piron
Jess Blatchley, Singing Teacher and Jazz Singer
Amy Bebbington - Director of Training bij Association of British Choral Directors
Stella Handley, Avocational singer
Jess Blatchley, Singing Teacher and Jazz Singer
She couples this with her techniques that allow one to manage things like performance anxiety with much greater ease. It’s a win- win as I have in the past 6 months started to perform at jam sessions and more. I love it!
Kim, Avocational Singer
What I also appreciate very much is her respect for every one of her clients / students.
Singer
Singer & Voice Teacher
Kelly Van Hove - Entertrainer focused on Soft HR & communication workshops / Vocational Musical Theatre Singer
Maud Retter - Speech therapist
Here’s the article “Theatrical Fog and Known Health Effects” written by Dr. Yolanda D. Heman-Ackah, originally published in the VASTA Voice (Volume 17, Issue 2, June 2022), shared here with permisson. I’ve added titles and images throughout the post to help clarify the concepts.
4 different types of theatrical fog
There are 4 different types of theatrical fog: smoke, fog, haze, and “low lying” effects. Inherent difficulties in understanding the health effects of these theatrical fogs exist because the health effects are dose dependent. A greater concentration of the theatrical fog in one’s immediate surrounding will increase the likelihood of toxicity.
It is difficult to study the health effects of theatrical fog as it is used in the theater because the exposure level for one given effect will be different for everyone in the theatrical cast and production staff depending on their proximity to the effect source, greatest density of the effect, and the ventilation in the area where they are located.
In an attempt to create standards for theatrical fog, the Entertainment Services and Technology Association (ESTA)’s Fog and Smoke Working Group developed practice recommendations for fog and smoke in open settings using a consensus-based standard.
This standard has been accredited by the American National Standards Institute (ANSI). The ESTA Fog and Smoke Working Group consists of a cross-section of entertainment industry professionals who represent diverse interests.
Because of issues related to concentration of the fog in a particular location, the proximity of the greatest density of the effect, and the surrounding ventilation, one should be cognizant of the fact that a fog can produce effects that pose health hazards despite the fact that they meet minimum ANSI standards for safety.
1. Smoke
Smoke is created by either pyrotechnic smoke cookies or smoke cartridges or by incense or HVAC smoke pens/pencils. The smoke generated consists of large solid particles produced from combustion.
Because smoke is created from combustion, the biggest health hazard is a thermal injury from the pyrotechnic. Fire extinguishers should always be nearby. Additionally, smoke is a respiratory irritant and can cause issues with vocal fold inflammation and reactive airways.
Symptoms of a toxic exposure may include hoarseness, cough, difficulty breathing, headaches, dizziness, drowsiness, tiredness, and mental confusion.
2. Fog
Fog is created by fog machines that dump glycol, glycerin, or a glycol/water mixture into a heat exchanger until the liquid vaporizes. The vaporized glycol produces a thick translucent or opaque cloud as its visual effect.
Fog from vaporized glycol or glycerin causes irritation and dryness of the nose, throat, vocal folds, and lower airways of the lungs, which can manifest as cough, dry throat, reactive airways, worsening asthma, and decreased lung function.
These effects can be both acute from acute exposure and chronic from repeated or long-term exposures. The fog created by fog machines can also leave a residue on exposed items, furniture, and the floor, which can be slippery.
3. Haze
Haze is a homogenous cloud used to reveal light beams. Haze is produced by a haze machine that atomizes the mineral oil using a spray pump powered either by electricity or compressed CO2. Haze can also be produced using a glycol/water mixture, often referred to as “water based” haze.
Chronic inhalation of mineral oil vapor can predispose to lipoid pneumonitis or pneumonia. Like the other glycol vapors, the water-based haze can also cause irritation to and inflammation of the nose, throat, vocal folds, and lungs. Haze can also leave a residue on the furniture, floor, and other exposed item that can be slippery.
4. Low lying effects
Low lying effects are produced by liquid carbon dioxide (CO 2 ) used in conjunction with theatrical fog machines. The liquid CO 2 is used to chill the fog, which causes it to stay within a few feet of the ground. As the fog warms, it rises and dissipates. Dry ice, which is solid CO 2 , can be dropped into hot water. In so doing, the heat causes the solid CO 2 to sublime immediately to the gas phase that appears as a thick white fog. A fan is used to direct the direction of the fog to create a rolling fog that lies low to the ground.
Liquid Nitrogen can be used in a similar manner. When liquid CO2, dry ice (solid CO2), and liquid Nitrogen are used to create fog, the fog is created from the transformation of the CO2 or the Nitrogen from a liquid or solid state into a gas state.
In this transformation, the percentage of CO2 and Nitrogen within air is increased and the relative percentage of oxygen is decreased. This shift in the relative percentages of CO 2 , Nitrogen, and oxygen in poorly ventilated areas can be toxic and cause headaches, nausea, vomiting, blurred vision, dizziness, shortness of breath, decreased cognitive function, and altered ability to reason to everyone in the environment who breathes the new gas mixture. In high concentrations, loss of consciousness and death can occur.
Ensuring adequate ventilation, including an adequate space for the fog to dissipate and for fresh air to enter the area is extremely important, especially for those seated in the orchestra pit or working at the base of the stage who are more likely to be affected by the thicker concentrations of these fogs.
Conclusion
Thus, there are some health effects possible with all forms of theatrical fog.
- The extent of the exposure, including the concentration of the fog material in the surrounding air, the length of exposure, and the ventilation in the area are all factors that determine the severity of acute health effects
- Chronic or repeated exposure can cause long-term vocal fold and airway irritation and inflammation.
- Limiting exposure duration and concentration and increasing ventilation onstage are factors that will help to limit health effects from theatrical smoke and fog.
- Glycol, water/glycol mixtures, glycerin, mineral oil, and smoke-based fogs are most likely to cause vocal fold, nasal, throat, and lower airway lung inflammation, dryness, and reactivity and should be avoided whenever possible in favor of liquid CO 2 , dry ice, or liquid nitrogen based fogs.
- Theatrical fog should be used in an area where there is adequate ventilation that permits the easy and quick egress of the fog and influx of untainted air.
REFERENCES
1. ANSI e1.23-2020, Entertainment Technology – Design, Execution, and Maintenance of Atmospheric Effects. ANSI Board of Standards, 1 Apr. 2020, Document number F&S/2002-3014r19.
2. Varughese S, Teschke K, Brauer M, Chow Y, van Netten C, Kennedy SM. Effects of theatrical smokes and fogs on respiratory health in the entertainment industry. Am J Ind Med. 2005 May;47(5):411-8. doi: 10.1002/ajim.20151. PMID: 15828073.
3. Moline JM, Golden AL, Highland JH, Wilmarth KR, Kao AS. Health Effects Evaluation of Theatrical Smoke, Haze, and Pyrotechnics. Equity Pension and Health Trust Funds. ENVIRON International Corporation. June 6, 2020.
In all of my teaching, technical skill, psychological support, and vocal health go hand in hand. What we practise in lessons is never just vocal fold closure or vowel alignment. It’s also about developing the awareness and confidence to take care of your voice and your overall wellbeing, whenever and wherever you need it.
In one-to-one online voice lessons, we’re building a resilient, sustainable instrument, along with the mindset and practical tools you need to navigate rehearsals, performances, and challenging environments with ease.
Book your Free Discovery Call – no obligation – to see how we can work together and whether you’d like to build this resilience alongside your vocal technique.
Pieter Van Hecke, Vocational singer
Bec Tilley, Voice Coach & Singer
Ariane De Dom, Avocational singer
Dr. Tracy Smith Bessette - Singer, Voice Instructor, Early Music Coach & Course Lecturer
Nele - Singer & Youth Library Worker
Susanne Vahle - Vocational singer
Kelly Van Hove - Entertrainer focused on Soft HR & communication workshops / Vocational Musical Theatre Singer
You learn to look for a solution and deal with your struggles yourself. It's not pre-made shit, it's to the point.
Esther De Bièvre - Recovery therapist
Janet Wilson - Vocational singer
Kenneth Ottoy, Singer of Plagiaat & Piron
Nele Willekens - Library youth worker
Diane Speirs - Singer & Voice Teacher
Bec Tilley, Voice Coach & Singer
Stella Handley, Avocational singer
Susanne Vahle - Vocational singer
What I also appreciate very much is her respect for every one of her clients / students.
Singer
Haike D'haese - Singer & Actress
She couples this with her techniques that allow one to manage things like performance anxiety with much greater ease. It’s a win- win as I have in the past 6 months started to perform at jam sessions and more. I love it!
Kim, Avocational Singer
Stella Handley, Avocational singer
Breg Horemans - Vocational singer
Kim, Avocational Singer
Esther De Bièvre - Recovery therapist
I leave our lessons feeling inspired and with new tools to use with my voice students. I particularly love that I now have language to identify and describe with more specificity the different kinds of sounds that live in pop/rock styles. Working with Sarah has made me a better teacher for my students!
M.J. Johnson, Singing Teacher and Vocal Coach
I highly recommend Sarah if you are looking for a voice specialist!
Gwendy - Vocational singer
Singer & Voice Teacher
Jess Blatchley, Singing Teacher and Jazz Singer
Jess Blatchley, Singing Teacher and Jazz Singer
Manon Campens - Singer
Amy Bebbington - Director of Training bij Association of British Choral Directors
Maud Retter - Speech therapist
As always, feel free to send me your thoughts, questions, and feedback in the comments below this blog, via the contact form or in the singsing! online community 
Cordially,
Sarah
Email from Joseanne Conceição, received in June ’24:
Thank you for sharing the post “Theatrical Fog and Known Health Effects”. I’m a victim of it. Last year, I got exposed a lot to it and I ended up developing an allergy to it to the point it cause an inflamation in my lungs and a temporary Asmath scenario. Your post was very important in my journey to show the doctors that the smoke do can affect the people’s health.
Even after 7 months since the last contat with the theatrical fog, I’m still having challenges to go back to my normal life: presenting tireness and dyspinea at any activity that demands more physical effort (such as washing my hair, washing the disshes or going on a small walk). I’m not even being able to sing yet cause I get tired after singing the first or second stroph.
Here in Brazil, the use of theatrical fog has become more commum in the last four to five years. Nowdays, it is present in church’s services, schools, et cetera. We also don’t have a regulation to certificate this chemicals or articles talking about the side effects of this kind of smoke. Because of it, the doctors that I went to would not connect the symtoms I had to the smoke. They told me that the fog was safe and could not affect the health. But I know what I went through and the only abnormal thing in my life was the fog (I had 9 allergic reaction to it in three months).
I started to search for the side effects of the theatrical fog in american websites and I found yours and it just gave me such a sense of relief. I was not crazy, other people suffered with it as well. I shared your article with my doctors and now they are considering the smoke as the cause of the inflamation in mu lungs. Thank you for sharing this knowlegde!
I’d like to get more people to have access to this information. People can be getting through the same thing I’m going through and they may never know that this kind of smoke can cause it.
So, I’d like to know if I can translate your article to Portuguese, so it would be available to more people?
I was a victim of it and my desire is to share this knowlegde to more people.
My best regards,
Joseanne Conceição