Not long ago I was asked by a student how to know which bell cover (a performing arts aerosol mask to cover the bell of an instrument) to buy for her music lessons and band class, or if she should make her own, and how long they last. Since, at that time, almost everyone in the area was still completely online and we hadn’t had to really think much of it yet, I did a little research. According to the NFHS Colorado Performing Arts Aerosol Study, MERV 13 filters are the minimum rated filter to use in masks. And while filtration is the most important part of any mask, there are other considerations to take into account as well.
LONGEVITY
As I understand it, the MERV 13 filters are good for one to three months of continuous flow. To envision continuous flow, think of the filter that you might find in a furnace (if you are a young person reading this, ask your parents if you don't understand). Some quick math shows that one 30-day month has 720 hours (I'll let you figure out how many lessons that is). Now, personally, I think using the same filter for the equivalent of one or more years (presuming you take that 720 hours and spread it out) is a bit gross, especially since the filter will collect moisture (you are blowing warm, moist air through it when you play), can sour if not stored properly (think potential mold growth) and washing a filter isn't really a good idea as it reduces its effectiveness. So, if you find your bell mask gets smelly or dirty, or if we find ourselves still having to mask longer term, you need to replace it. Also food for thought: a furnace air filter (that's what the MERV 13 filter really is) gets changed every 1-3 months regardless of whether or not the heater is running the entire time.
BUYING VS. MAKING
With regard to buying MERV 13 filter material to make your own inserts, I took a look at that and am not convinced it is the right thing to do. I was not able to find a vendor that I was comfortable purchasing from. There was just way too much conflicting information about whether or not what you order is what you actually get, as well as whether or not what you get is actually made of materials that are safe to use in masks (you don't want fiberglass in your filter, for example). Considering we are all trying to be safe I figured that, personally, I would just go with known companies that sell filtered masks and/or pre-cut filters.
So that leaves us with purchasing masks with preinstalled filters. There are two companies which I know are selling MERV 13 bell masks. I am sure that there are more, I just don't know who else does. One of the companies sells bell covers with sewn in filters, and the other sells bell covers with replaceable filters. You will need to decide which one works best for you.
REPLACEABLE FILTERS OR NOT
The first company makes bell covers that do not have replaceable filters, so once it is used up (remember that one to three months mentioned above?), you need to replace the entire mask. For me, this alone is a deal breaker. Going further, this company takes orders online and has a variable turnaround time. For a woodwind bell cover, their product costs roughly $7 (more for larger bell covers).
The second company makes bell covers that do have replaceable filters. So, as long as you keep the actual mask in good shape, you can continue to use it as long as you change the filter every one to three months. This company sells their products in local and large chain music stores, as well as online, and they are readily available with little to no wait. The initial price for a woodwind bell cover is a bit higher at roughly $20 (more for larger bell covers), but the savings is in the longevity. Replaceable filters (also for woodwinds) come in packs of five for $20.
COST
Even though it looks like the bell covers with the replaceable filters are more expensive than the built-in filters, they really aren’t. Let’s break it down: one $20 bell cover plus a pack of five replacement filters (six total filters) comes out to $40. Six $7 bell covers with non-replaceable filters comes out to $42. What about another five filters after that? $20 for filter replacements and $35 for non-replaceable filters. Over time, the bell covers with replaceable filters are less expensive.
CONCLUSION
While both companies claim to have the MERV 13 filters, in the end I recommended that this student purchase the bell cover with the replaceable filter. The availability and lower cost (over time) made the most sense to me.
DISCLAIMER
I am not a doctor nor am I a filter specialist. The statements in this article are not intended to diagnose, treat, or prevent any illness, nor are they intended to endorse any company (which is why I did not name the companies or provide links to products). I encourage all students and readers to do their own research into the products they wish to buy prior to purchasing them. Where health matters are concerned, I strongly encourage you to speak with your physician prior to making decisions.