By Todd Edelman

The City of Davis and many other local government entities are distributing masks for "free". While there have been some shortages and limited availability of masks for children, a big problem is counties and cities have different recommendations about use, e.g. because of risks of carbon dioxide build up for some, that some will fit poorly, but most often that the priority should be staying indoors – i.e. that masks should only be used if one HAS to go out.

There are these designer masks available. As far as I can tell this type became very popular due to the chronic air pollution in, e.g., Beijing. People there are wearing masks every day, and want to show off and also de-medicalize the issue via its most obvious sartorial component. (3M, after all, makes workplace safety equipment, and I joked earlier that thanks to child labor laws they make no masks for small faces – by the way I recommend their slightly upgraded N95 with the valve for Co2 exhaust….).

Anyway, the problem here is that these fashion masks – just like any masks that look like proletariat undergarments – encourage people to be outside, who should not be… they are a palliative for a much bigger structural problem, of course also here in California during latest and greatest wildfire fallout disaster.

Overdue edit on 8/6/2021: The general recommendation now seems to be that you select the US EPA conversion, not the LRAPA conversion.  See, e.g., this post, which also explains that the AirNow data, while perhaps more accurate than PurpleAir, can have a fairly significant delay, which (to my way of thinking) defeats the point of accuracy if conditions are changing rapidly, especially if they are changing for the worse.  You might think air quality is good when in fact it is not.

Edit on 9/30/2020, since this old post continues to get a lot of attention: I recommend that you check out this article about reconciling the official government numbers and Purple Air's.  One exciting development is a "a pilot project of what some may consider to be the Holy Grail of air quality maps: combined readings taken from PurpleAir’s low-cost sensors and those from official government monitoring devices, all in a single map."  -RM

A lot of people are now turning to PurpleAir.com for real-time air quality measurements.  But everyone should know that, in their default setting, they show higher PM2.5 readings than the government's sensors.  To obtain more realistic readings, use the box in the lower left hand corner of your web page to change the conversion from "none" to "LRAPA."  You can read more about the LRAPA settings here and here. 

Please pass along this information.  Our situation is serious and people should be appropriately cautious (stay inside if possible, use filters if possible, obtain N95 masks from the Davis Fire Department), but no purpose is served by thinking that things are worse than they actually are.

(Screen shot in this post taken at around 4:10 PM, Thursday, November 15).

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