Questions for NEA's PSI

There are many conspiracy theories around on why the PSI readings seems so low when the our own eyes and noses are telling me otherwise.
Many facebook posts have highlighted that the PSI readings are seemingly low in the morning, and reduces the need for workers to stop work, and reduces pressure for MOM to announce Stop-Work orders.

Random Facebook Status #1-

I love how the psi lowers in the morning as people are getting ready to go to work and rises drastically when they are all safely in the office. Meanwhile the view outside looks exactly the same.

Random Facebook Status #2

8am psi was 158. 9am is psi 256. The psi machine starts working at the  same time as everyone else! I love it!

I dont believe in conspiracy theory, I think all government agencies do treasure Singapore lives.

But I do believe NEA needs to revamp this PSI systems and answer some hard questions.

1) Why use a 3-hour PSI? Why not just update the immediate newest PSI?
I know that a 3 hour average is to smooth out any outliers, ie sudden spikes or sudden drops. But what is the point of smoothing out any spikes? Even if it is only a one time spike in the PSI, it is definitely enough to let the public know and takes the necessary precaution.

The 3 hour averaging will just reduce any large spike in readings, and reduce the public's precautions.

2) Why  PSI only includes PM10 and not PM2.5?
http://www.nea.gov.sg/psi/

PM2.5 includes the smaller, finer particles that are more damaging to human health. If breathed in, it can be lodged deep in the lungs and stays there...
PM2.5 is definitely much more of a health hazard, why is this information not broadcast, or included in the PSI?
Yes we can get the PM2.5 readings in NEA website, but without as much publicity as PSI in our media (TV, radio, newspaper), this danger is rather understated.

3) And yes, NEA still needs to silence the conspiracy theorists
Why are the PSI readings so low in the morning and why does it spike upwards once workers start working? If there is any technical difficulties in using the PSI machines, please do update and let us know. Rumours spreading everywhere does not help at all.
I was informed that the PSI machines pumps in air and takes 15 minutes to measure the particles, and there are technical difficulties involved.

Let's sing to this haze song... just to bring some cheers...