From 63f07c0374fc2527f095d07154500c4adc899d19 Mon Sep 17 00:00:00 2001
From: Camron Blackburn <camron.blackburn@cba.mit.edu>
Date: Sun, 22 Mar 2020 21:50:39 -0400
Subject: [PATCH] Update README.md

---
 README.md | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/README.md b/README.md
index b98ef14..9c0c3cb 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,8 @@ so we're targeting filter material able to block particles with minimum ~0.25um
     - CMAD: count median aerodynamic diameter
 
 
-### conventional test methods
+## Filtration efficiency tests 
+### biological challenge particles
 - Henderson apparatus: generates closed circuit microbial aerosols from a Collison nebulizer at a controlled humidity 
    - Collison nebulizer - generally a pneumatic atomizer [^collisonNebulizer]
    - ![](henderson_apparatus.png)
@@ -36,9 +37,24 @@ so we're targeting filter material able to block particles with minimum ~0.25um
     -   Bacillus atrophaeus : 0.95-1.25um, 10^7 cfu in challenge [^DIYmask]
     -   Bacteriophage MS2 MCIMB10108: single strange RNA ~20nm diameter, 10^9 pfu in challenge [^DIYmask]
     -   E. Coli phi174 [^VFEreport]
+- Viable particle cascade impactor (andersen sampler) for collecting particles, incubating them for a day or two, then counting bacteria or phage growth 
 
 performance difference between pleated hydrophobic filters and electrostatic filters??
 
+### non-biological challenge particles 
+- send colliodal spheres through atomizer (what's the diff between nebulizer and atomizer?) and use optical particel counter (OPC) to determine filtration efficiency
+- ASTM standards uses latex spheres. could potentially use gold particles 
+- charge neutralizer recommended - but Lorena said viruses are typically polarized so maybe charge neutralization could be ignored initially 
+
+
+## shopping list 
+- nebulizer for aerosolization [^nebulizer_selection]
+    -   three-jet Collison nebulizer? 
+- impinger for collection 
+- wet and dry thermometer / hygrometer for humidity 
+- andersen sampler?? could be nice to bin different size particles - six-stage viable particle cascade impactor
+
+
 ### Resources
 [^DIYmask]: University of Cambridge [DIY mask efficacy testing](https://www.researchgate.net/publication/258525804_Testing_the_Efficacy_of_Homemade_Masks_Would_They_Protect_in_an_Influenza_Pandemic)
 [^filterPerformance]: AR Wilkes [The bacterial and viral filtration performance of breathing system filters](https://onlinelibrary.wiley.com/doi/full/10.1046/j.1365-2044.2000.01327.x)
@@ -49,13 +65,3 @@ performance difference between pleated hydrophobic filters and electrostatic fil
 [^VFEreport]: [Nelson Laboratories: Viral Filtration Efficiency (VFE) at increased challenge level](https://gitlab.cba.mit.edu/pub/coronavirus/tracking/uploads/164d119b5a7a5751c685a6677378668a/ER_2235600_Attachment_5_Viral_Filtration_Efficiency.pdf)
 [^nelson]: [Nelson lab filtration test](https://www.nelsonlabs.com/testing/bacterial-viral-filtration-efficiency-bfe-vfe/?industry=medical-devices&category=protective-barriers-material-performance)
 [^nebulizer_selection]: [Nebulizer selection from CH tech](http://chtechusa.com/Manuals/Selecting%20the%20Model%20and%20Configuration%20Instructions.pdf)
-
-## needed for testing apparatus 
-- nebulizer for aerosolization [^nebulizer_selection]
-    -   three-jet Collison nebulizer? 
-- impinger for collection 
-- wet and dry thermometer / hygrometer for humidity 
-- andersen sampler?? could be nice to bin different size particles - six-stage viable particle cascade impactor
-- 
-- 
-- 
\ No newline at end of file
-- 
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