The situation in the contra dance world with "fragrance free" is a mess. Many dances have very strict policies, but they don't emphasize them. Which means they're not dances that work for people who need the strict policies, but at the same time are putting attentive and careful people through a lot of work in avoiding common scented products.

For example, if you look at the Concord Thursday homepage or FB event there's no mention of a fragrance policy. At the end of their Code of Conduct, however, there's:

Consider: We are a fragrance free event. Please do not wear scented products.

This isn't just asking people not to wear perfume or cologne: products not explicitly marketed as "fragrance free" generally have at least some scent. Trying to pick some very ordinary products that don't mention that they're scented on the front, when I read the ingredients they all list both "fragrance" and several scented ingredients (camphor, limonene, benzyl salicylate, etc):

A dance organization I help run, BIDA, recently ran a survey. Several of the questions asked how folks felt about using far UVC and glycol vapors to reduce risk from COVID, flu, and other airborne pathogens. There were 208 respondents, which is pretty good!

When asked how their attendance would change if BIDA used these interventions, the response was:

A pandemic that's substantially worse than COVID-19 is a serious possibility. If one happens, having a good mask could save your life. A high quality reusable mask is only $30 to $60, and I think it's well worth it to buy one for yourself. Worth it enough that I think you should order one now if you don't have one already.

But if you're not convinced, let's do some rough estimation.

Entropic Thoughts recently reanalyzed the data I'd shared on the relationship between mask requirements and dance attendance we've seen at BIDA. They conclude:

Other sources account for most of the variation in dance attendance, and masking only plays a small part. The amount of the total variation contributed by masking requirements is 5 %. This number is called the coefficient of determination, and its square root is the correlation: 0.21. This correlation is low enough that we cannot conclude that masking has a significant effect on attendance.
...
"But it still looks like masking has an effect!!" It does. It's just that if the effect is there, it is small enough that we cannot statistically prove an effect with just 44 dances. Assuming the coefficient of determination really is 5 %, and we are aiming for a traditional significance level of 0.05, the sample size curves tell us we would need over 80 dances to be sure of the effect of masking.

The approach they took in their post involves some statistics that make assumptions about the distribution of the data. While these assumptions may well be right, now that we have fast computers we can often use simulations to avoid this. I decided to have a go at analyzing this data with a permutation test.

We planned to trial far UVC and glycol vapors at the BIDA contra dance last night: these are two options (beyond masks and ventilation) for reducing infectious aerosol inhalation. Both worked without issues.

I set up the far UVC Aerolamp on the stage, slightly angled down, primarily aiming to clear the air above the dancers:

I'm working out the logistics for trialing triethelyne glycol for pathogen control at a contra dance, and I need something to put the liquid glycol into the air. I'd initially been thinking of using a fog machine, but after discussion with friends who work in the area it sounds like an ultrasonic humidifier would work better. Instead of using heating and cooling, these use vibration, and put out much smaller droplets.

I got a random cheap humidifier on Amazon ($30) but (a) TEG is more viscous than the water its designed for and (b) its output is probably higher than I need. I decided I'd dilute the TEG to resolve both of these.