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Respirator Considerations

Another year, and California is burning.

I’ve taken advantage of the recent fires to perform more respirator trials. I use the respirators when getting around town on my bicycle, which provides a good analog for any aerobic activity, allowing me to evaluate things like breathability, humidity within the respirator, and how well the seal performs when contaminated air is being blown over the respirator at high speeds. I’ve found there are certain characteristics that I desire in a respirator.

Rating

The standard respirators that are most worth considering are N95. The “N” designates that it is not resistant to oil. The “95” designates that it filters 95% of particles 0.3 microns or larger.

After the BP oil spill in 2010 I purchased a P100 respirator. These respirators filter 99.97% of particles, and are “strongly resistant” to oil. They are large, bulky cartridge respirators that are great to keep at home, but you are not going to carry them around.

Recently I purchased a box of R95 respirators. These are more similar to the N95 than the P100, but are “somewhat resistant” to oil. They have a service life of 8 hours in environments with airborne oil particles, which is long enough for me to get to my P100 respirator. Unfortunately the R95 respirators are quite a bit thicker than the N95. They could be easily carried in a bag, but they are too thick to fit in my PPE kits (without moving to a larger aLOKSAK). I’m splitting the R95 respirators between home and work, but will continue to carry N95 respirators in my kits.

Back in 2007, when I first started researching respirators, I came across an adhoc study comparing these ratings against common household materials:

I recently assisted in a study to determine how available materials compared to P-100 respirator cartridges. Cartridges were opened, the contents removed, and a series of different materials were attached to the cartridges. The cartridges were installed onto standard North full-face respirators. A Certified Industrial Hygenist performed fit testing on the mask assembly using a standard quantitative fit testing machine, the one that compares particle counts inside the mask to ambient air particulate counts.

The materials tested were:

  • coffee filters, 1 layer;
  • t-shirt fabric (knitted fabric), folded into 8 layers, wet, dry, and oiled with petroleum jelly;
  • bandanas(woven fabric), folded into 8 layers, wet, dry, and oiled with petroleum jelly;
  • a HEPA vacuum cleaner filter, dry.

We boiled the cloth to shrink it before testing.

The performance of the coffee filter, HEPA filter, and the dry fabric was terrible. Abysmal. Worthless. Bad.

The wet fabrics were a bit better, but still bad. Why firefighters use wet bandanas to filter smoke is beyond me. They are practically worthless.

The HEPA filter was so moisture-resistant that the mask fogged up to where you couldn’t see out. And it didn’t perform that well. Perhaps its stiffness made the seal leak, it really should have done much better.

But the 8-layer oiled bandana and oiled t-shirt performed about 80% as well as the P-100 filter, and in fact passed about half the tests. This makes it equivalent to about a N-90, which is 90% as good as a N-95 filter. It was nothing short of amazing how well the oiled fabric filtered air.

Now it’s interesting that there is a report (page 1, page 2) from WW1 that a doctor on a troop ship made everyone wear oiled gauze masks, and did not lose a single person on the trip across the Atlantic.

Using an old-style cloth surgical mask and oiling it with petroleum jelly increases its filtration efficiency something like 1000 times. And oiled cloth filters actually filter better the dirtier they get, until they clog up. They are used in high-perforance cars.

Oh, and I suppose I ought to admit it was my kid’s science fair project.

Harness

Most respirators either have a single continuous harness that goes around the crown of the head and back of the neck, or two separate straps. I’ve not noticed a significant difference between these two options, though the single continuous harness can easily be adjusted for smaller heads with a single knot.

The two-piece harness is usually attached to the respirator via staples, the penetration of which may reduce the efficacy of the respirator, but only if the puncture results in a tear.

When staple punctures tear holes in the filter medium, the concentration of particles leaking through those openings is considerable and resembles face seal leakage… The findings of this study suggest that stapling head straps directly onto the filtering material of a respirator has the potential to create leaks in amounts similar to that of face seal leaks.

I look for a textile harness. Cheaper respirators use thin rubber bands. For single use these are adequate, but they snap if you are frequently donning and doffing the respirator.

Valve

A valve to vent exhalation is critical. Non-vented respirators are useless to me. Even if all you’re doing is sitting around not moving, the non-vented respirator will build up humidity over time, making long-term wear quite uncomfortable. Add in any physical activity and the process is accelerated.

At a minimum the vent should be closed at the top of the respirator. This prevents the warm, humid air from moving directly up and fogging your eyewear. On some respirators, the vent is closed on both the top and sides, forcing the exhaled air to escape downwards only. This is desirable.

Non-vented respirators are appropriate in healthcare environments when sterility needs to be maintained. That is to say: where you are concerned about your exhalation impacting the sterility outside the respirator, not the other way around. Vented respirators meet the same protection requirements as their non-vented counterparts.

If you’re worried about keeping your operating theater sterile, get a respirator without a valve and embrace the suck. Otherwise don’t.

Fold-Flat

I want to carry the respirator, which means I need to be able to fold it flat. There are two variants of fold-flat respirators: those that fold vertically along the center, and those that fold horizontally.

A center fold respirator provides more volume across the front of the face. When a respirator fits properly and provides a good seal, it should collapse slightly due to suction when inhaling during aerobic activity. When wearing a center fold respirator, this collapse happens along the cheek area. I find I tend not to notice it. With a horizontal fold respirator the collapse is more likely to happen across the front. The respirator touches my lips with each heavy inhalation, so I constantly notice it. I do not think there is a functional difference here, but it is a factor in long-term comfort.

A horizontal fold respirator can be more comfortably pulled down below the chin. A center fold respirator can not (unless perhaps you have an unusually long neck). If you need to temporarily remove the respirator – perhaps to take a drink – it can still be pushed down, such that the nose clip rides on the chin. I find this uncomfortable for more than a brief period of time. When the air quality index (AQI) is red or worse (151+), I generally want to wear the respirator whenever I’m outdoors. When the AQI is orange (101-150), I don’t feel I need a respirator if I’m just walking or standing outdoors, but I do want it when I’m breathing heavily. It’s in these conditions that I appreciate the ability to wear a horizontal fold respirator pulled down on my neck. I can easily (and quickly) pull it up when I begin breathing more heavily (ie, when I get on the bike). With a center fold respirator I’m more likely to temporarily store the unused respirator in a pocket, increasing the time requirement to don it.

Horizontal fold respirators place the valve in the center. On center fold respirators, the valve is offset to one side. When using horizontal fold respirators, I find that close-fitting eyewear is more likely to fog if I’m not moving (when moving more than a few miles per hour, air flow across the eyewear eliminates any fogging). I experience less fogging with center fold respirators. I’m not sure if this is due to the position of the valve – perhaps the offset valve encourages the warm, moist exhalations to be vented to the side, rather than immediately up to the lenses – or due to the seal. A center fold respirator, I find, provides a superior seal across the top of the face because the respirator naturally wants to pinch the bridge of the nose and hug the cheeks.

Color

Most disposable respirators are white. Some come in gray. The fashion market offers respirators in dark colors and patterns. These look cool, but I prefer white. White shows dirt, encouraging me to replace the respirator more frequently than I probably otherwise would. Despite the lack of a NIOSH standard for respirator reuse (including those labeled “single use” by the manufacturer), particle build up on the surface of the respirator will increase pressure, which will increase leaks. If you’re using the respirator out of concern of influenza or flu, the color of the respirator is probably irrelevant. For smoke and other pollutants that leave visible residue, white may be better.

Recommendations

3M has a large, sprawling product line that seems to have a lot of redundancy and overlapping offerings. The 3M Aura 9211+/37193 checks most the boxes and is the nicest horizontal fold respirator I’ve used. The material is about 1.5mm thick, and the valve sits about 15mm off the face of the respirator at its tallest point. The wings easily fold in, allowing the respirator to fit in a small aLOKSAK for one of my PPE kits. Because of how the respirator folds, when the wings are folded in, the thickest part of the respirator excluding the valve is 13mm. I feel the respirator is a bit loose around my chin and jaw, but the seal still seems effective. Condensation becomes visible on the outside of the valve, which shows you it is working. The material that makes up the upper portion of the respirator has a perforated layer between inner and outer shells, which I imagine contributes to the respirator’s breathability, but this upward facing exhaust causes the respirator to fog eyewear a bit more than it otherwise would. The center portion of the respirator has some sort of stiff interfacing that feels a bit like a thin foil. This stiffness seems to prevent the suction collapse I usually experience with horizontal fold respirators (although the perforated upper portion and the loose fit on the lower portion of the respirator could also contribute to this). The harness is two pieces, textile, and stapled.

Condensation on a 3M 9211+

The Dräger X-plore 1760 is a vented, center-fold R95 respirator. It is the highest quality respirator I’ve tried. Being an R95, it is too thick to fit into my PPE kits. The material is 3mm thick. Folding along the center line, and then folded again such that it would be the right dimensions to fit in my desired aLOKSAK, it ends up being 18mm thick (excluding valve), which doesn’t work. The valve sits about 11mm off the face of the respirator. If you want some oil resistance, and don’t need to fold the respirator more than once, this is an excellent option. I stay significantly more comfortable underneath this respirator than others. It has a tight seal on my face that provides good suction on inhalation, and you can hear and feel the valve flutter on exhalation. Condensation becomes visible on the outside of the valve, which shows you it is working. I have attempted to fog the lenses of my Rudy Rydons while wearing this respirator, and failed. They only fog when I break the seal of the respirator to adjust its placement. It has a single-piece, continuous, textile harness.

Condensation on a Drager X-plore 1760

After discovering how great the 1760 was, I purchased the Dräger X-plore 1750, hoping that it would be the same thing but thinner. That ended up being exactly what it is. This respirator is the N95 variant, which explains the difference in thickness. It is just under 2mm thick. Folded to fit in the aLOKSAK, the thickest part of the respirator excluding the valve is 7mm. I find myself leaning toward center fold respirators, and this is a perfect center fold N95. If you just want to buy a box of respirators and be done with, I’d recommend getting these.

Dräger also produces a version of the 1760 with activated carbon that I would like to try. If it isn’t any thicker than the standard 1750, the extra odor protection provided by the activated carbon could be a nice bonus. My respirator budget is depleted for now, and I have more than I need for a while, so you’ll have to wait until a future fire season for a review of that one.

My P100 respirator is a 3M 6391. It has not seen much use, as I’ve yet to be in an environment where it is needed. I’m as happy as I can be given the limited wear time I’ve logged with it over the past 8 years. You’ll have to wait until the next oil spill before I can give a meaningful review. One consideration worth keeping in mind when shopping for a respirator like this is that the height of the nose piece can interfere with some eyewear.

A Personal Air Filtration System

Another year, and California is burning.

After Napa burned to the ground last year I decided to invest in an air filter. I ended up with a Coway AP-1512HH, which seemed like the right size for my small apartment, and came with a good recommendation from The Wirecutter.

Coway AP-1512HH

The unit has three different filters: a pre-filter intended for large dust particles, hair, and the like; a carbon filter to remove odors; and a HEPA filter that does the heavy lifting.

The pre-filter I clean by vacuuming every 4-6 weeks (when I think of it). The carbon filter I’ve never attempted to clean. The HEPA filter has a 12-month lifespan. The air quality sensor is also supposed to be cleaned every couple months. I’ve cleaned this once, after about 8 months of service, when I noticed that the unit was constantly registering a high pollution level that I disagreed with. Cleaning the sensor immediately fixed the problem.

The Coway is supposed to light an LED when the HEPA filter needs replacing. My unit has been in use for 12 months now, and that LED has never turned on. I’m not sure why that is, but since the replacement cycle is yearly, and the LED alert is nothing more intelligent than a timer, I simply offloaded the problem to taskwarrior.

$ task add project:air due:2018-12-15 recur:yearly wait:due-8weeks "replace Coway AP1512HH filter set (3304899)"

The filter detects pollution and, when placed in automatic mode, adjusts the fan speed appropriately. The current pollution level is indicated by a ridiculously bright LED that can light up a whole room. I’ve placed a piece of tape over this. This is necessary if the unit is in the same room that you sleep in.

Coway AP-1512HH Control Panel

I’ve enjoyed using the filter throughout the year. It takes care of cooking smells, so that I’m not smelling my dinner all night. I assume the copious dust I clean out of its pre-filter would otherwise end up in my lungs. At its lowest two settings it is quiet enough to leave on overnight, providing pleasant airflow even if I don’t need the filtering. During the cooler months when I don’t want the extra airflow, I keep the unit in “eco” mode, which disables the fan module when no pollution has been detected for 30 minutes.

However, I had not felt that the cost of the unit justified what I was getting out of it, until California caught fire again. Since last Thursday San Francisco has been inundated with smoke, requiring the use of a mask during outdoor activity. But I’ve had clean, clear air indoors. I tried turning the Coway off for a few hours when the Air Quality Index was in red. The difference was immediately noticeable. I don’t have any measurements to measure the efficacy of the unit on wildfire smoke, but in my qualitative experience, it makes a huge difference.

Living in an area where air quality can become tainted – which, given climate change, seems to be most areas of human habitation – I think a personal air filtration system is as important as water filtration and storage. It is the kind of thing you won’t spend much thought on until you need it, at which point its presence or absence can make a significant impact on quality of life.

I have not used any other air filter, so I’m not sure what the best option is, but I have no complaints about the Coway AP-1512HH beyond the LEDs. This past week has moved it from the would-not-purchase-again category firmly into my would-purchase-again-immediately category.

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A Reminder that Eneloops are a Good Buy

Recently I went through my Eneloop batteries, cycling those that I keep in devices. I decided to purchase another pack of AA and AAA batteries, not because I needed to replace any but because I have more devices to power. After ordering the new batch, I realized this was the first time I had purchased AA batteries in seven years. (I had purchased AAAs more recently – three years ago – again not to replace any, but because I needed more.) My seven year old batteries are still in service and hold on average 85% of their factory charge. I don’t intentionally cycle through the full set of batteries, so some sit in storage holding their charge for years.

It doesn’t get much better than that.

I started using Eneloop rechargeable batteries in 2011. The following year I purchased a programmable charger, allowing me to track the health of my batteries in git. When not in service I store the batteries in a Pelican 1060.

Suunto M-9

I wanted a compact compass for an upcoming trip. Not a real orienteering compass, but something more than a button compass like Suunto Clipper. I ended up with the Suunto M9. At 1.5 inches in diameter, it is roughly the size of a small watch. It features 5 degree gradations and a sighting notch for rough bearings. A ratcheting face with orientation indicators allows you to set direction of travel. To work with the sighting notch and window, the compass card uses a reverse numbering scheme: instead of looking at 12:00 to read your bearing, you look at the 6:00 position. This is unintuitive at first, but easy enough to adjust to. Suunto advertises the compass as waterproof, and the bastion of truth that is the Internet claims it to be divable to at least 200 feet. Tipping my scale at 10 grams, the M9 packs an impressive amount of capability for its miniscule size and weight.

Unfortunately, the Velcro strap it comes with is garbage. It’ll hold it on your wrist, but it is uncomfortable and I question the longevity and security of the attachment after prolonged exposure to mud, sweat, blood, and the tears of my enemies. Fortunately the M9 has 19mm lugs, which matches an old watch I had about a decade ago. I dug out the NATO Regimental strap I had used on that watch, threaded it onto the M9, and now I have a wrist compass I can feel pretty good about.

I only wish it had a global needle, but that would probably require a larger housing.

Suunto M9

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SKD PIG Alpha Gloves

I’m on my third pair of SKD PIG Alpha Gloves. My previous two pairs have lasted around 15 months. This current pair is on track for the same.

The gloves are lightweight, synthetic, and highly dexterous. While wearing them I am able to tie my shoes, pick up a penny, and load a .22 caliber magazine – all reliable tests for the dexterity of any glove. I wear the PIG Alpha Gloves every day on the bike, and am happy with the 15 month lifespan given both the intent of the glove and their cost.

They are a mechanics gloves, and should be compared to things like the Mechanix Original Covert. The Mechanix were my every day glove prior to purchasing my first pair of PIG Alpha Gloves in 2014. I find that the dexterity is the same in both, but the PIG Alpha Gloves are more comfortable and a bit more durable.

SKD PIG Alpha Glove

  • SKD PIG Alpha Glove
  • SKD PIG Alpha Glove

The greatest selling point of the PIG Alpha Gloves over most Mechanix models is the touch-screen compatible fingers. In earlier generations, SKD accomplished this by sewing silver thread into the index finger. This worked when the gloves were new, but quickly failed as the thread became dirty and began to fall out. SKD fixed this a couple years ago by replacing the silver thread with a conductive synthetic suede on the index finger and thumb. I’ve found that this works great, and continues to do so until the whole glove fails.

When the glove does begin to fail, it does so in the fingers. The fingers and palm are covered in ventilation holes, which slowly grow as the glove is abused. After this I find the stitching in the fingers will start to blow out. At that point I move on to the next pair.

The lightweight, synthetic materials of the PIG Alpha Gloves stay acceptably cool in hot weather. They’re not as cool as wearing no glove, and my hands will sweat wearing them, but I’ve never found them so uncomfortable that I want to take them off. The gloves provide no protection from the rain, but they dry within a few hours of being soaked.

Paracord loops on each cuff allow the gloves to be easily secured when not in use. I cut the D-ring off of the left shoulder strap of my Litespeed and replace it with an ITW Grimloc. This is where the gloves live when I’m off the bike.

SKD PIG Alpha Glove

The gloves do run a little small. I wear a size medium in just about every glove out there. In the PIG Alpha Gloves, size large fits me perfectly.

I purchased a pair of Magpul Core Technical Gloves back in 2015 when Magpul got into the glove game. These are meant to be in the same category of lightweight, dexterous, mechanics glove as the PIG Alpha Gloves and Mechanix, but I found them to be inferior to both offerings. The lack of adjustability in the wrist makes them annoying to put on and take off. The thicker material cuts down on dexterity (while probably improving durability) and makes them too warm to wear in hot weather. The touch screen finger tips are unreliable when the glove is dirty.

Dexterity and durability are inversely related in a glove, but the SKD PIG Alpha Gloves find a happy medium for my use. For poor weather conditions or mountain excursions, I still like gloves like the Kuiu Guide Gloves, but the mechanics glove is a better style for every day use. Right now I think the PIG Alpha Gloves are the best glove of this type on the market. I’ll continue to wear them every day and replace them every 15 months.

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Tactical Chucks

The Altama OTB Maritime Assault Boots are a great pair of everyday footwear. Modeled off of Chuck Taylors, they’re a fairly simple concept: a 1000D Cordura upper, large rubber toe cap, and low-profile outsole with minimal lugs.

Altama OTB Maritime Assault Boot

The boots provide excellent grip on wet and dry concrete. Altama claims to use some sort of special sticky rubber, though it feels like typical shoe rubber to me. It is not noticeably sticky, like Five Ten’s rubber. The lug pattern is not ideal for dirt and mud, but for an everyday urban shoe I have no complaints. After 6 months, my boots shoe a reasonable amount of wear.

I bought them in a size US 10 / EUR 43, which fit me perfect. In most brands I alternate between a US 9.5 or 10, which usually translates to a fairly consistent EUR 42. They tip my scale at 29.3 oz (832 grams) for the pair.

The laces that come with the boots are ridiculously long. Unless you tuck them into the boot, they’ll catch on things. They constitute a hazard on the bike. I replaced them with Lawson Toughlaces, laced in a double helix and tied in a bowknot. Lawson’s laces are just heavy pieces of Technora with metal aglets on the end. Abrasian resistant, fire resistant to 932 degrees Fahrenheit, and with a breaking strength in excess of 1,000 lbs – you can saw through restraints all day with the Toughlaces and they will still probably last until the heat death of the universe. I have them cut to 54” for these boots.

Altama OTB Maritime Assault Boot

Altama ships the boots with removable polyurethane insoles. This material makes sense for the intended water application of the boot, but I worried that they would be hot and uncomfortable for my more pedestrian use. So far I’ve not found that to be the case, but I’ve only had the boots since the end of September, so I can’t comment on their comfort in hot weather.

Neither the insole nor the boots themselves have any arch support, but they are not zero drop. There’s a heel to toe differential that feels like it is probably in the 6mm-8mm range. All of this lift, however, comes from the insole. After replacing the laces, my second modification was to purchase a pair of Ortholite Fusion Insoles. These are completely flat. The size 10 insole fit perfectly in my boots without any trimming, transforming them into zero-drop footwear. Unfortunately, the boots really want a slightly higher volume insole. With the Ortholites installed, I get a small amount of heel slippage that cannot be addressed by lacing. This is not an issue for my typical everyday wear, but would become problematic if hiking.

Altama OTB Maritime Assault Insoles

I still find myself switching between the stock polyurethane insoles and the Ortholites, but I lean toward the Ortholite being a more comfortable choice. It’s worth experimenting with them if you find high heels uncomfortable.

The Altama OTB Maritime boots feel like they come out of a latter Gibson novel. Black, minimal branding, fairly gender-neutral, and able to be worn, to a general lack of comment, during any year between 1945 and 2000.

A Better Towel

Discovery Trekking‘s Extreme Ultralight Travel Towels are the best quick-drying, packable towels I’ve found. Typical microfiber towels are scratchy and quick to stink. The Extreme Ultralight Travel Towel forgoes microfiber for Polartec Power Dry with a Polygiene treatment. They are soft, pleasant to use, and resistant to funk.

It’s use may be somewhat unintuitive for those who cut their teeth on traditional towels. Rather than the typical rubbing action, the Extreme Ultralight Travel Towels work best when you pat yourself down.

I bought my first of their towels in 2015. I go to the boxing gym in the morning and shower before work, so I’ve used that single towel multiple times per week for the past 3 years. It has no smell. In fact it is indistinguishable from the new towel I just bought last week.

I prefer the towels in size medium, which measure 28” by 34”. It’s the right size to dry off my whole body, though if I had long hair I may opt for the larger size. The only shortcoming of the towel is that it has no loop to hang it from, but this is easily remedied with a piece of paracord and some thread. On my scale, the size medium (with paracord hanging loop added) weighs 3.4 oz (98 grams).

I own the towels in charcoal and olive brown. The olive brown color is similar to that shown on Discovery Trekking’s website, but is what the rest of the world would call coyote brown. The charcoal color is nothing like what they show on their site. In their images it appears black, but in reality it is a grayish green, similar to foliage green, but slightly darker. I like it.

Normally I would not care about the color of a towel, but I note the colors here because the fabric is comfortable enough that I actually use the towel as a scarf – something which I cannot say about any microfiber towel. It provides warmth in cooler weather, and sun protection in hot weather. The Power Dry fabric is rated at UPF 15. This dual use makes it easy to justify the towel’s miniscule weight and volume in a pack, ensuring you always know where your towel is.

Any man who can hitch the length and breadth of the galaxy, rough it, slum it, struggle against terrible odds, win through, and still know where his towel is, is clearly a man to be reckoned with.

Douglas Adams

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Rudy Project Rydon

I’ve used a pair of Rudy Project Rydon Stealth glasses as sun and safety glasses for about five years now. They’re a great eye protection system for active wear, and I think are especially attractive for those who require prescription eyewear. The Rydon offers an adaptable system with interchangeable lenses and full coverage, in a lower profile compared to popular tactical eyewear systems like the Revision Sawfly, Oakley M Frame or ESS ICE.

Rudy Project Rydon System

The temples and nosepads of the Rydon are made from an pliable rubber material that lets the user adjust them however they want. You can have straight temples or hook them down behind your ears. You can move the nosepads to get the right height and clearance on your face. I find that both adjustments largely stay in place after being set. If they do move, it is simple to reset them.

Safety & Durability

The only difference between Rudy’s “Stealth” and non-“Stealth” line is the ANSI Z87.1 rating applied to the frame. Z87.1 is the standard for eyewear protection that will be familiar to anyone who has worn safety glasses or so-called “tactical” eyewear. It describes, among other things, impact resistance. The Rydon lenses are interchangeable between Stealth and non-Stealth variants, and certain lens selections have their own Z87.1 ratings. The Stealth frames are made from a different material than non-Stealth. The non-Stealth Rydons fail to meet Z87.1 standards due to how they shatter1.

Unfortunately, Rudy has not certified the Rydon for MIL-PRF-32432, the military specification for ballistic eyewear.

As you might expect, the Rydon have proven to be very durable. I’ve used them regularly over the past five years. I shoot in them, I crash bikes in them, and I’ve been punched in the face more times than I can count in them. They’re none the worse for wear. Certain lenses have minor scratches, but none that I notice when I’m actually wearing them. The frames themselves are like new. The rubber material does not absorb sweat and odors, which is a complaint I’ve heard of Oakley’s “unobtainium” rubber temples.

ImpactX

Rudy is well known for their ImpactX lenses. They describe it as being a “bullet-proof, transparent, and light-weight material capable of providing superior protection, reliability and longer lasting performance than polycarbonate”. It is what Apache windshield panels are made out of, which makes me feel good about myself2.

ImpactX is actually just Rudy-branded NXT. NXT is a variant of Trivex. I’m not sure what the difference is between NXT and Trivex. It may be that NXT is just a specific branding of Trivex. I do know that the Z87.1 impact protection that NXT/ImpactX claims is a property of the Trivex. Trivex gives equal protection.

Trivex is a polymer that was introduced as an alternative to polycarbonate. Traditionally, most safety glasses are made out of polycarbonate. When you get a prescription insert from Revision or ESS and have them fill the prescription, the lenses they’re putting in are polycarbonate. “Plutonite” is Oakley’s proprietary brand of polycarbonate. Trivex offers equal impact protection, but has a lower Abbe number than polycarbonate, which translates to superior optical quality.

Trivex is slightly more expensive (polycarbonate costs ~$40, Trivex ~$50). Trivex also has a slightly lower refractive index, which translates to Trivex prescription lenses being slightly thicker than polycarbonate. But Trivex has a lower specific gravity, so the Trivex lenses will be slightly lighter than the equivalent polycarbonate, despite the added thickness.

There’s nothing rare or special about Trivex. Everyone does it. You can bring any set of frames into any optometry office and tell them you want to put Trivex lenses in it. As long as your prescription fits the frame, they can do it. The resulting lenses will meet or exceed Z87.1, even though your optometrist likely isn’t going to get them certified for the Z87.1 stamp.

Photochromic

The ImpactX lenses, in addition to offering impact protection, are also photochromic. Photochromic lenses darken when exposed to ultraviolet radiation. Having a clear lens in a pair of safety glasses is critical for indoor work, and being able to use the same lenses as sunglasses outdoors keeps the overall price down. It is also helpful for transitions. If you start out in the sun and then go inside, or the clouds roll in or the sun sets, your optics quickly respond without you needing to take time to remove the glasses or swap lenses.

When I first purchased the Rydon system, one of the lenses I included was the ImpactX photochromic clear-to-black. This is a neutral lens that offered 18-78% light transmission. A few months ago, I purchased Rudy’s ImpactX-2 photochromic clear-to-black lenses. These offer 9-74% light transmission. In addition to the change in light transmission, ImpactX-2 also reacts faster and is supposed to respond slightly better to non-UV light3.

Other Lenses

While the ImpactX lenses are the only offerings from Rudy with the Z87.1 stamp, the company does offer some other lens options.

Rudy’s Polar 3FX is their polarized lens solution. Polarized lenses reduce glare, which is useful on water and snow. I have a pair of Polar 3FX brown lenses. At 15% light transmission, these offer about the same protection as my old Julbo Micropore glacier glasses. They’re a great supplement to the ImpactX photochromic lenses, and are light enough that I am happy to carry them as a secondary option on backpacking trips for use above the tree line.

The third lens I went with is what Rudy calls Racing Red. These are a high contrast red lens with 28% light transmission. A contrast lens in something like red or yellow is a great option for hazy days when it isn’t bright out and you don’t want much light reduction, but you find yourself squinting from the glare4.

Of the three lenses (or four, since I now have two of the photochromic clear-to-black lenses), I use the Racing Red least of all. They’re great in certain conditions, but the ImpactX(-2) lenses work well in all conditions, so I find that I can just leave them in the frame all the time and never think about it. Plus, Z87.1.

Prescription

Rudy has a few options for people who need prescription lenses. The option that I’ve gone for is the Optical Insert. I used a similar setup back in the day with Revision Sawfly eyewear and their insert, but I think Rudy does it better. While this kind of dual lens system does result in a slight degradation of optical quality, it means that you only pay for the prescription once. Being able to purchase multiple non-prescription lenses that sit in front of the prescription lens is the only thing that makes this kind of multi-lens system tenable.

Rudy offers two different carrier styles: a full metal frame and a “rimless” option.

When I first purchased the Rydon system I went with the full metal frame. It has served well over the years. Like the Rydon frame, it still functions like new. Occasionally a punch in the face will cause the insert to be knocked out of the Rydon, but that hasn’t caused any damage to the carrier, and it only takes a second to pop it back in.

This past spring, when I bought the new ImpactX-2 lenses, I also wanted to purchase another carrier to have my new prescription put in it. This time around I tried the “rimless” model. The “rimless” carrier is not actually rimless: the lenses are held in place by a thin wire that goes around the circumference of each lens. This can result in a thicker lens. With a rimless carrier, the lens need a groove cut into it to accept the wire. Prescription lenses are thinnest on the inside (near the nose) and thickest on the outside. If your prescription is weak enough that the outside of the lens is not already thick enough for the groove to be cut, the thickness will need to be increased.

I’ve not found that the lenses in my rimless carrier appear any thicker than the ones in my old carrier, but that’s something that you may want to keep in mind when deciding between the two carrier options.

When you’ve received the carrier, you can take it to any optometrist to have your prescription lenses filled. Finding an optometrist who has some experience with this kind of setup – whether they are actually a Rudy dealer or offer some other sport brand with an insert system – will like behoove you. With my first pair, I used a Rudy dealer. The optometrist that I used when filling the new carriers this year was not a Rudy dealer, nor had they ever dealt with something like this before. However, they actually grind their lenses in house, which is something I’ve never seen before. When placing the order I was able to talk with the lab manager who would actually be making the lenses, which gave me confidence that I wouldn’t be wasting my money5.

For the prescription lenses, I went with polycarbonate. With a dual lens system like this, both weight and thickness are a concern. While Trivex would have been lighter, we decided that the thinner polycarbonate would be better suited for my prescription. The polycarbonate prescription lenses would be behind the Rydon’s ImpactX(/NXT/Trivex) lenses, so I don’t have much concern about the lower impact resistance.

This time around I went with an anti-fog coating, which I did not have previously. While it was rarely ever an issue, I did occasionally experience fogging with the old lenses. It usually happens when walking into a sweaty gym when it is cold and dry outside. It’s not really the time of year for me to be able to evaluate if the anti-fog coating is doing anything on the new lenses.

I think an anti-glare coating on the prescription lens is unnecessary. The tinted Rydon lenses should take care of that problem whenever necessary.

I did also go with an edge polish on the new prescription lenses. Previously I opted to forgo that option with the old metal carriers, but with the rimless carrier I thought that it would help maintain a lower profile look – both from the outside looking in and the inside looking out. I think it was a smart decision.

Notes

  1. Personally, I think that wearing sunglasses which are not Z87.1 rated is stupid and a waste of money, outside of certain specialty requirements. Eyes are important. You can't fight what you can't see, unless you are a time travelling samurai.
  2. When you get down to it, why wouldn't you protect your eyeballs with the same technology used in gunships?
  3. Traditionally, one of the shortcomings of photochromic lenses is that they don't work well in cars. Windshields filter UV light. ImpactX-2 is supposed to handle that a little better. I can't comment on that -- I spend very little time in cars.
  4. I also believe that having a contrast lens that you can wear when it isn't necessarily bright enough for normal sunglasses is useful to combat color-based advertising intended to condition us to better suit our extraterrestrial overlords.
  5. With most optometrists you end up dealing with the people who sell lenses. Talking to someone who actually makes the things lets you dip into a different knowledge base.