so i purchased astm level 3 mask for me my parents and my sibling because they always used a lower quality mask. i’m wondering what’s the difference between them, the mask i bought is only 1 layer so i’m a bit scared because i work in a high risk area and study in the same area.
edit: my mask is actually 3 layered but it was a thin mask so i thought it was a single layer, thanks for comments thoguht
I bought a pack of 3M astm f3502-21 masks and then read what that standard means. I am confused about whether it is filtering particulates that I could be breathing in or not.
I think that everything I’ve read indicates that it helps filter what comes FROM me and not what I come in contact with?
I also figure it’s better than nothing but just wondering if anyone can help clarify.
I'm a structural engineer attempting to be a statistician for a project and I am struggling. I'm performing a statistical evaluation of lumber engineering properties and following ASTM D2915. Section 4.4.3.2 discusses calculating a parametric tolerance limit (PTL) and standard error of the statistic (SE). I am investigating normal and lognormal distributions. If normality is assumed these equations apply:
PTL = X - (K * s) where X is mean, K is a tabulated confidence level factor, and s = standard deviation
SE = s * sqrt((1/n) + (K^2)/(2*(n-1))) where n is the sample size (s and K same as above)
ASTM D2915 does not give separate equations for a lognormal distribution, so I assume that I take the natural log of the individual data points and compute mean and standard deviation using the same equations for assumed normality. Hence, PTL and SE are then computed the same way as shown above with the natural log of the data points . However, the SE seems incorrect. For example, if I perform my lognormal analysis starting with the raw data in different unit systems, I get the same SE which seems illogical. This results in the SE/PTL ratio being different for the lognormal analysis depending on unit system where the logical expectation is that the ratios would be the same.
I must be doing something wrong and I'm hoping that someone could steer me in the right direction. Any help would be appreciated.
Hey, i'm new at welding and don't know if it's possible OR recommended to weld A36 steel with a cold rolled steel.
You may be seeing masks promoting their “ASTM Rating” and are not sure what that means. What is ASTM? Who even gives this rating? Should I care??
Below is an easy-to-read breakdown of what exactly the ASTM rating is and how it may or may not apply to you.
What is an ASTM? ASTM rating?
https://preview.redd.it/y4t4b9hmas281.jpg?width=1310&format=pjpg&auto=webp&s=841828d3fce079d49ba556cd778ab40f7bf46f2f
ASTM International (American Society for Testing and Materials)
An organization that creates and sets standards for a range of products, materials, systems, and services used by people performing their jobs every day WORLDWIDE.
They focus on:
-PPE (Face Masks)
-Construction materials
-Plastics/Rubbers/Textiles
-Construction
-Ships and Marine tech
-more
ASTM created a 3-level rating system specifically for surgical masks using the following 5 Performance Indicators:
- Bacterial Filtration: How well it stops bacteria
· Differential Pressure (Breathability): How easily air passes from one side of the mask to the other
· Sub-Micron Particulate Filtration: How well it stops smaller particles like air sprays, VIRUS
· Resistance to Penetration by Synthetic Blood (Fluid Resistance): How well it acts as a barrier to blood, spit, splashes)
· *mmHg can be viewed as the amount of pressure behind fluid
· Flammability: All fabrics of natural or regenerated cellulose, as well as certain types of finished and unfinished fabrics made from other natural or synthetic fibers, are combustible. Class 1 is normal flammability.
Once a mask is tried against these 5 tests, they will be assigned a level:
· Level 1 mask: able to filter out ≥ 95% of bacteria, ≥ 95% of 0.1 µm particles (Like VIRUS), and provide fluid resistance to simulated blood at 80 mmHg
· Level 2 mask: able to filter out ≥ 98% of bacteria, ≥ 98% of 0.1 µm particles (Like VIRUS), and provide fluid resistance to simulated blood at 120mmHg
· Level 3 masks: able to filter out ≥ 95% of bacteria, ≥ 95% of 0.1 µm particles (Like VIRUS), and provide fluid resistance to simulated blood at 160mmHg
**THE ONLY DIFFERENCE BETWEEN LEVELS 2 and 3 ARE HOW WELL THEY PREVENT FLUIDS FROM PASSING THROUGH THE MASK
Do you NEED to buy ASTM rated masks?
ASTM rated surgical masks do a good job of reducing the risk of transmission/infection, however, it is important to note that that because of the loose fit, even le
... keep reading on reddit ➡I have a A394-08 Table 4 Shear Strength for a 1/2" bolt and want to know if I can use the value give or should I be multiplying it with a reduction value.
