Thread: Want your DC checked for invisible dust?

Originally Posted by mic-d

Bob, page 2 of this document may slay a sacred cow about muffs and plugs...

http://www.e-a-r.com/pdf/hearingcons/earlog8.pdf

I dunno . . . . . a publication on a .com site that sells ear plugs - I'd find it a bit more believable if it was a peer reviewed publication.

Peer reviewed tests have demonstrated that even when fitted by trained professionals the dB ratings for plugs are not as good as the claims by the manufacturer, especially when they are repeated taken in and out. There are similar problems with muffs not fitting correctly e.g. with my new glasses I find they prevent muffs making a good contact. For long periods of chainsaw use I go for both plugs and muffs, but for a 10s burst with an angle grinder and dirty hands, I find muffs are just easier.

Originally Posted by BobL

I dunno . . . . . a publication on a .com site that sells ear plugs - I'd find it a bit more believable if it was a peer reviewed publication.

Peer reviewed tests have demonstrated that even when fitted by trained professionals the dB ratings for plugs are not as good as the claims by the manufacturer, especially when they are repeated taken in and out. There are similar problems with muffs not fitting correctly e.g. with my new glasses I find they prevent muffs making a good contact. For long periods of chainsaw use I go for both plugs and muffs, but for a 10s burst with an angle grinder and dirty hands, I find muffs are just easier.

Got some references? When you get done on dust maybe you can do hearing...

Originally Posted by mic-d

Got some references? When you get done on dust maybe you can do hearing...

I'll leave that for SoundMan.

Certainly a pro ear plug document....it has the timerity to try and down play the ear infection issue with earplugs......it most certainly is an issue, both with plugs and with muffs.

They may be calling "reported" infections, which will always minimise the figures......let me tell you after wearing plugs for 7 to 9 hours a day for 5 days running, my ears are inflamed & itchy....AND I use 2 or 3 clean sets in a day.

Like all such documents there is a difference between the products they chose to test and those that are commonly used in the market.

That document I think you will find is over 10 years old.

Google the specs on peltor H10s and you will find they have higher attenuation than the "high performance muf they call.........the H10 is quoted as a 30db muff but appart from the couple or 3db dip at 2K that all muffs seem to have that stay above 40db attenuation at 1khz and above, and like all mufs they fall over badly below 500Hz.

The H10s are about as good as it gets in a conventional muff

as for ear plugs, not may people are prepared to spend much on high performance ear plugs, even fewer are prepared to clean non disposable earplugs.
I have a pair of non disposable precision earplugs that cost me over $35, that I used to wear doing pub rock and roll and going to concerts

Most people use the foam disposables.....which are not shabby, but..they may spec up above 40db in the easy to achieve 4 and 8Khz.....but they are about 10 db short of the H10s at 1khz.
they redeem themselves in the low frequecies....they are about 6db better than peltor H10s at 125hz

That is with ouyt accounting for deviation and propper fit

The real problem with earplugs is the variation and consistency of fit.......the H10s quote 2 to 3db of stadard variation, where the foam plugs quote arround 7 to 10 db of variation.

Ear plugs simply don't work well on some people even if they get fitted properly...and most don't get fitted properly.
Personally I have to realy try hard to get foam plugs to fit.

I have worn earplugs for more than 9 hours in a day many times...believe me I'd rather wear a good ear muff if it is sufficient.

I cant say I feel the need to use heavy attenuation when I use a chain saw, I consider than a relativly low noise risk item and generally use one of my lighter sets ( I own 5 sets of muffs)....Bob mate do you need a new muffler.

As for the glasses issue...I wear glasses whenever I am vertical....it causes me no problem with muffs.....but I only wear peltors, the pads mould well and I probely have groves in the sides of my head.

cheers

Originally Posted by soundman

I cant say I feel the need to use heavy attenuation when I use a chain saw, I consider than a relativly low noise risk item and generally use one of my lighter sets ( I own 5 sets of muffs)....Bob mate do you need a new muffler.

The saw I'm running is a 120 cc MS880 with a modified muffler and it usually sits on this chainsaw mill
The ally pipe on the front right of the powerhead is the exhaust outlet.



The exhaust outlet has been increased from 14 mm to 19 mm. Typical continuous cutting time is 3/4 of a full tank, and I go through 6-8 tanks in one day.
I haven't put a dB meter on it - I should do that sometime.

And pardon me Bob, but it is peer reviewed. It's somewhat ironic that you try and cast into doubt someone else's information (that's actually peer reviewed) on an internet forum - cognitive bias or what?

excerpt from this page:

"EARLogs are peer reviewed by independent experts prior to publication. This highly acclaimed series has appeared in eleven journals, is read in over 36 countries, and is utilized by the U.S. armed forces, OSHA, CAOHC, and more than 70 universities as educational materials for hearing conservation training courses. Moreover, it was heavily cited by the Mine Safety and Health Administration (MSHA) in their revised 1999 noise regulation. Selected EARLogs have been translated into Danish, German, French, Portuguese, and Swedish and others have been reprinted as contributed technical articles in magazines and journals in the U. S., Canada, Europe, Australia, and Brazil."

And just because there is a post on the woodwork forums that one person has sore ears from wearing ear plugs that does not make it a clinical study.

Originally Posted by mic-d

And pardon me Bob, but it is peer reviewed. It's somewhat ironic that you try and cast into doubt someone else's information (that's actually peer reviewed) on an internet forum - cognitive bias or what?

excerpt from this page:

"EARLogs are peer reviewed by independent experts prior to publication. This highly acclaimed series has appeared in eleven journals, is read in over 36 countries, and is utilized by the U.S. armed forces, OSHA, CAOHC, and more than 70 universities as educational materials for hearing conservation training courses. Moreover, it was heavily cited by the Mine Safety and Health Administration (MSHA) in their revised 1999 noise regulation. Selected EARLogs have been translated into Danish, German, French, Portuguese, and Swedish and others have been reprinted as contributed technical articles in magazines and journals in the U. S., Canada, Europe, Australia, and Brazil."

And just because there is a post on the woodwork forums that one person has sore ears from wearing ear plugs that does not make it a clinical study.

My experience in dealing with research publications by commercial companies is that review by independent experts could mean anything. Anyway, it doesn't matter who reviews them, these docs are still published on a commercial site with a vested interest - so there is a clear conflict of interest that they cannot get around. They can make the all the claims they wish that it is independently reviewed but as they are their own publishers the final contents can still be "Arranged" to suit their interests. The information they contain may well be accurate, but if so, why don't their scientists just publish these in the open scientific literature?

If my students were to base critical research decisions on these documents I would require them to look elsewhere.

I have to agree.......getting a truly independent acedemic opinion in the US is nearly impossible, everybody has an axe to grind and large corporate sponsorship is the norm in US acedemia.

If you want a document reviewed, you make damn sure you know how it is going to review before you allow it.

If you want ya eyes opened on this matter, get a coppy of "Toxic sludge is good for you", it details the depth and extent of corporate, acedemic and government nepotism in the US society.

There are plenty of compaines that produce or sponsor large volumes of acedemic material that is very widely circulated....of course it all plays to the companies interests and it is all "peer reviewed".

In many areas, the only peers that are availabe to review, come from the same philisophical school.

In the US there are educational instututions who's primary purpose is to produce professionals with a specific view. This my be aligned with a religeon, a ploitical party or one of many corporate interests.

Even in this county and this state it happens.......in certain areas if your course work does not tow the line or the faculty view or the facultie's taste, you do not get marked well, if you do not do well or are not regarded as having the right view in the course, you do not get a job with the limited number of employers, if you do not have experience with one of the limited group of employers and have the right view you do not get to teach...and the circle continues.

So the only people working have one outlook.

The facts and the comparison between earplugs and earmuffs is very well known and it is supported by the manufacturer's published data.
There have been minor inprovements and chages over the years but the issues remain the same.

There is a limit to how much low frequency attenuation can be achieved with any earmuff..it maxes out arround the 20db below 500Hz, good well fitting plugs alone can do around 10db better.

There is a limit to how much mid range attenuation 1 to 2 ish khz can be achieved with earplugs and that is arround the 30-35db, good well fitting conventional high performance muffs can do arround 10db better in this range

High frequencies in the 4Khz and above is realitvly easy...stuff ya fingers in ya ears and you will get 40db at 8K

Overall attenuation is also limted to different figures across the range.

nothing can change that because the limitations are due to the head and the ear.


cheers

Well as I said, put up some references from the literature that you reckon we can trust.

The earlog documents are used by OSHA around the world. They wouldn't use bad information would they?

Who says Earlog documents are used arroud the world.....Earlog.......and explicitly by whom and exactly what for.

In Australia you can check the figures for the hearing protection item, they should be tested acording to Australian Standards and the figures should be pretty reliable.

If you want go and cough up the $$$ required to access the standards...knock ya self out.

AS1269 "Acoustics - hearing conservation" and AS1270 "Acoustics - hearing protectors" should get you started.
Then you can move onto the durth of material from state and commonweath regulators
start with the "QLD workplace Health & Safety Act" and the "Workplace Health and Safety (noise) Compliance Standard 1995" and move onto the various government advisory publications.

All the figures for Peltor are easily available on line and pretty well any half decent hearing protection item will have a standardised set of figures, measured & displayed in accordance with Australian Standards printed on the box.

We have no need of an horn blowing, american, self published, publication that is slanted to make the sponsors product look good.

We have a standarised system of measurement plenty of non promotianly engineered independent information available.

knock ya self out.

cheers

Originally Posted by soundman

No sorry but some people are too lazy to think or are they just plain dumb or do they just not care.

Why would anybody go a buy pleated cartrige filter, that probably cost as much as the dust extractor its self, the primary purpose being that it is a better filter than a cloth bag and simpy leave the coth bag fitted to the bottom of the dust extractor.

"This highly efficient filter is an excellent upgrade to your existing FM-230 dust extractor. Pleated cartridge filters are far more efficient than even needlefelt filter bags. This one is manufacturer rated at 1 micron. It will also suit many other brands of 1 hp dust extractors. The unit is cleaned by rotating the handles several times. Doing this rotates a rubber beater inside that removes settled dust from the pleats. Unit needs to be used with plastic collection bags in place of cloth bags. These are available in packs of ten in the relevant sizes for each machine. Pleated cartridges not only provide vastly enhanced micron filtration, the pleating also increases the surface area by over 700%. This in turn also increases the CFM rate." (Carbatec website)

Filter $169
FM230 $199



For a start - I am guessing that a good proportion of DC users are not so concerned about the particle filtering in an OHS sense, and just literally want a *Dust* *Collector*. Ie - shavings in bag good, shavings on floor bad.

Bob and others have written plenty on the cfm effects of ducting choices, and many will spend time and effort into maximising the cfm delivered to machines by their DC system, so there is no reason not to think that, for some, choosing a pleated bag is folded into that thought process.

I don't know the answer to this: Would the plastic bag drop the total cfm of the DC (over a bottom cloth bag)?
If so then that could be another part.

Or just inertia.

Finally I could imagine some people not 'trusting' the plastic bag in so far as thinking it might be weaker, subject to major tearing, less re-useable, vulnerable to UV, ... practical concerns.

Particle filtration concerns are not necessarily the major concern of all DC users ... people on these fora might be an unrepresentative sample ... ie more conscious of the issues.

Cheers,
Paul

Originally Posted by pmcgee

"

For a start - I am guessing that a good proportion of DC users are not so concerned about the particle filtering in an OHS sense, and just literally want a *Dust* *Collector*. Ie - shavings in bag good, shavings on floor bad.

Bob and others have written plenty on the cfm effects of ducting choices, and many will spend time and effort into maximising the cfm delivered to machines by their DC system, so there is no reason not to think that, for some, choosing a pleated bag is folded into that thought process.

I don't know the answer to this: Would the plastic bag drop the total cfm of the DC (over a bottom cloth bag)?

Of the huge sample of 5 DCs I have tested with pleated filter (PF) top and cloth bag (CB) bottoms the main reason they all bought the PF was not to reduce dust but because they did not want to clean their top bags - they never actually clean the bottom bag - they just empty it and put it straight back on. Even though the flow loss from using a plastic bag bottom is negligible the the users have not even thought about this.

Today I decided to investigate our (very expensive European) house vacuum cleaner. It has a HEPA filter in it with a DOP rating of 99.99% (no micron rating provided).

When I tested it about 3 weeks back it had an almost full bag and was spewing out dust like there is no tomorrow.
The bag was now full, I repeated the test and got the same result - that is the blue line. For all particle size ranges the VC puts out more dust than it is sucking in - hence the negative efficiency ratings.

As I said in that previous post the vacuum cleaner was in need of some TLC so I
- opened up the cleaner and checked for cracks, misalignment of various openings etc - nothing obvious.
- pulled out the HEPA filter and knocked out the dust (about a tablespoons worth) - then I gently blew the HEPA as clean as I could get it with a compressor - holding the nozzle well back from the filter so as not to damage it.
- I washed the HEPA prefilter and wiped down all the rubber seals with a wet cloth and then armourall
- I blew out and wiped down all internal surfaces holding the HEPA filter and bag with a wet cloth and once dry I blew off all the loose dust.
- inserted a new paper bag.

The net result was then the red line. For the 3 biggest particle size ranges the VC was now putting out less dust than it was sucking in.
The graph is shown on such a coarse scale that it is difficult to see but the
1 - 2 micron range is 35% efficient
2 - 5 micron range is 71% efficient and the
> 5 micron range is 92% efficient
So, better than before but still no better that an $100 no name special VC for those particle size ranges and worse on the finer stuff.

I was somewhat intrigued where all those fine particles are coming from.
From what I could gauge there are two possibilities
a) either the machine is making them from incoming larger dust particles
b) or it is making them internally from trapped dust or the machine itself (I have seen this before)

To rule out a) I stuck the inlet nozzle under my 800 cfm HEPA room air filter under which my particle detector reads 0 for all size ranges.
The result was the green line - if measurement uncertainty is taken into account the red and green lines are essentially the same.

This result rules out fine dust being made out of incoming dust. To see if the machine would eventually clean itself over time I left both running for 15 minutes and there was no change over that time. It therefore appears the very expensive VC is just making all this dust all by itself. In numerical terms the wretched thing spews out 25 times more fine dust than it sucks in. One thing I should add is that on this VC the motor is located after the HEPA.

This is not the first time I have seen this with expensive HEPA filtered VCs we have a similar VC at work that behaves in the same way from when it was new and the excess very fine dust was tracked to the motor brushes.

Cheers

One thing that concerns me in some vacuum cleaners, one is the point at which the bag mates up with the incomming connection.

I cant see how it possibly seals in some...the pipe just seems to poke thru the hole in the bag good luck there.

A very old machine (an all alloy R2D2) I have, the plastic flange on the bag is forced over the inlet pipe and could reasonably be expected to seal.

The other thing to consider, is the motor in your vac, thru flow or bypass motor.

Thru flow motors, the air stream flows thru the entire motor.....thus the functional air flow and the cooling air flow are the same.
On a bypass motor the functional airflow and the cooling airflow for the motor are seperate.

Thru flow motors are cheap and nasty, remnant dust gets into the armiture and the bearings and the motor grinds it self to death bathed in fine gritt........having pulled one of these motors appart they can harbour large amounts of dust in the motor, the blowers remain relativly clean.

I suspect that, a lot of dust is moist as it is vacuumed up.....not much is realy dry..when the dust is moist it sticks to the armiture, as it dries it comes off providing a convienient slow release function.

Thruflow motors also over heat if the air flow is stalled.

A bypass motor will have a seperate functional air outlet and a cooling inlet and outlet.

Vac motors are angry little things and you may be seeing dust from the brushes and comutator in addition to dust convieniently stored in the motor.

If it is a bypass motor you can identify the air systems and test them seperately.

Most domestic vaks have thruflow motors.

Only the better industrial vaks have bypass motors.

Another thing I am suspicious of is how well the paper bags are sealed......do they leak at the seams and the corners.
The new superfunky bags synthetic bags that our new wonder cleaner uses are welded at the seams.

cheers