Talk:HEPA

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as defined by the DOE That's not clear whether its the definition of the abbreviation or the definition of filtering efficiency.

The three mechanisms in "In a HEPA filter, particles are trapped (they stick to a fiber) by one of three mechanisms; diffusion, interception or impaction" don't explain themselves. Looking the words up won't help. Perhaps they have specialised meanings in context, but that isn't made clear here. --ToobMug 16:57, 29 December 2005 (UTC)

I agree. The three mechanisms are explained here: [Mechanisms of Filtration http://www.tsi.com/AppNotes/appnotes.aspx?Pid=33&lid=439&file=iti_041] User: Zaytran 23:28, 29 December 2005 (UTC)

Someone suggested adding more information on "the original HEPA filter." Superm401 - Talk 17:41, 23 April 2006 (UTC)

In the first paragraph a flow rate is quoted as 85 L/min. I'm sure these filters come in a variety of sizes and they'll all handle a different flow rate.

85 L/min is the theoretical flow rate for purposes of testing whether a filter meets HEPA qualification. Mention of this in the 2nd paragraph was not intended to specify the operational limits of HEPA filters, though there is likely some bearing. Do reword this if you find it misleading or augment the content with more detail from other references than the one given.

I wouldn't mind seeing some information/references, ideally based on graphs, regarding how the efficiency varies with air flow, and how this applies to different applications such as HVAC (uni-directional) vs. respirators (bi-directional, though either both directions or solely inhalation can be of interest).

Of minor concern is that the HEPA mechanisms more or less duplicate content in the article respirator. I couldn't think of how else to add the content at the time so just left it that way. The respirator list is more extensive as not just HEPA is discussed. -Onceler 00:34, 30 September 2006 (UTC)

Contents 1 HEPA-type/HEPA-like 2 Graph 3 hepafilter.com 4 correct expansion of the abbreviation 5 links

[edit] HEPA-type/HEPA-like

The air purifier article basically says "BEWARE of those that say 'HEPA-type'", but can anything be known about a filter that is labeled as such? What do they mean by "HEPA-type"? It seems they would be limited in saying that by false advertising laws unless it had something in common with real HEPA filters. What is that something? — Omegatron 21:21, 25 October 2006 (UTC)

"HEPA-like" or "HEPA-type" filters are just as you said: non-conventional advertising practice. That "something" is maybe only the shape (pleated) and these filters actually yield a lower efficiency. True medical HEPA filters are all laser-tested and should remove 99.97% of all particles greater than 0.3 microns. The test is done using DOP and if not passed, they are not issued a certificate. Usually, "HEPA-like" filters have an efficiency of 95% (as advertised by some "fairer" companies) but no one really knows the actual efficiency unless tested. The Vindictive 08:27, 12 April 2007 (UTC)

[edit] Graph

So it picks up particles above and below 0.3 um? We should have a graph of that, like [1] — Omegatron 21:41, 25 October 2006 (UTC)

[edit] hepafilter.com

Perhaps we should delete this link? It does not provide any information about hepa filters, but seems mostly to be a commercial site. VitaminE 23:35, 17 December 2006 (UTC)

[edit] correct expansion of the abbreviation

Correct expansion of the abbreviation (acronym) is "high-efficiency particulate-arresting" (filter).

Yes, and when I corrected the article to the correct acronym, it was reverted. What gives? —Preceding unsigned comment added by 128.2.161.180 (talk) 17:41, 31 October 2007 (UTC)

I suggest finding a modern, authoritative reference giving that expansion. The expansion used most commonly, and therefore most likely correct in the absence of a clearly authoritative source to the contrary, is "High Efficiency Particulate Air." Since "HEPA is commonly followed by the word "filter" this certainly makes sense. Pzavon 00:20, 1 November 2007 (UTC)

[edit] links

This is helpful: the CFR that covers N100 filters http://www.cdc.gov/niosh/pt84abs2.html comment added by User talk:Quincy8Boy on 20 June 2007

Both N/P100 and N/P99 would have been called "HEPA" in the past. This NIOSH regulation establishes a designation scheme for particulate filters that moves away from, and in fact does not use the term "HEPA" at all. Pzavon 02:53, 21 June 2007 (UTC)