Modify a standard vacuum-cleaner so it's well grounded to eliminate static charge (WARNING:
This is only for those who know about earthing/grounding, who know that their mains-wiring in the house is proper and has a good ground an no voltage potential between neutral and ground! (You can test that with a cheap digital volt-meter) In North America 50+ year old homes often lack a separate ground wire network!
Often they still use a hot-neutral pair. Then you avoid grounding via the ground-prong but: If there is central heating: A radiator or its water-pipes can be used for ground! If you don't know about grounding, stay away from it!
This is also not for the faint-hearted, worrier and of course not for those with shaking/insecure hands)
It is not recommended to use a normal vacuum cleaner to suck dust etc. away from the sensor, focusing-screen or AF-sensors!
The reason is the danger of static charge which
can kill chips in your Pentax DSLR (or any other digital camera).
There is a reason why this method is not recommended for cleaning PC's, motherboards, processors etc. as well as for the fan on your processor.
Some say the danger with a PC/Laptop is due to the fan speeding up and thus producing higher voltage than it is driven with.
But this is not the case, any fan inside a computer is protected with a resistor, diode or 2 diodes preventing this. I have measured my fans in my PC's with 3Volts/DC, so this is not really the danger
The danger is static charge which can kills chips etc.!*
Antistatic wriststraps won't do much, even if the vacuum-cleaner would be grounded it wouldn't help (most aren't anyway!). The resistance of your body is too high that it would ground the hose/nozzle because it isn't made out of "static-conductive" material (special polypropylen as used in ESD Vac's). The argument "But I did it and it worked" is not very valid. Yes, maybe it's 50:50, maybe even less, but why risk the damage of your DSLR if you can solve this with a few bucks and some DIY?
But if you use an antistatic wriststrap AND the grounding of the hose/nozzle, then you are on the save side.
Many might have noticed how hair can take on static charge when dried with a normal hair-dryer! The same static charge does built up within a vacuum-cleaner.
If you'd suck in magnesium dust particles, they'd ignite just through the static charge (so don't)
THE DIY-ADAPTER: Parts needed:
- fine stranded insulated wire about 2-3 m long
- cutter to take some insulation off
- mains-plug according to your country you live in (one has to be able to open that plug so you can insert the wire!)
1. Carefully take off ca. 5-6cm of the insulation on one end of the wire
2. Carefully take off ca. 0,5cm of the insulation on the other end (this will be connected to your mains-plug)
3. Connect this shorter end to the ground/earth connection of your mains plug (usually the middle one) Make really sure you know exactly which one is ground! If you connect it to the wrong one you'd risk your life!
With some plugs it is also possible to remove "neutral" and "hot", so just neutral plugs in into the wall-socket.
If you have central heating and radiators, you can connect the wire also there! For this you need the wires also long enough, 0,5cm won't do.
a) US Nema-5 plug: 
I don't have a Nema-plug so I marked the ground/earth pin which takes on the short end of the wire!
b) UK-mains-plug: 
make sure you wrap some rupper or plastic around the wire were it is fixed to the exit of the plug so it really sits tight and can't be pulled out!
c) EU-mains-plug: 
EU-plugs have the option for the old French main-sockets with the earth-pin sticking out in the socket as well as the German earth connection.
d) Suisse-mains-plug: 
as you can see, here I didn't connect/solder the wire yet. This is how I started but now one of my sons is using the original.
This is the hose-adapter I got for my DIY ESD Vac: 
It connects to the main hose if any vacuum-cleaner, mine was a Miele.
I prefer this thin nozzle which can take on other heads but I used it like this:
The adapter in use: 
Of course you don't touch any part inside your Pentax! But I have successfully cleaned many Pentax bodies this way.
If you are worried that there would arise a static discharge between the camera and the copper strands (which I never experienced ever and I have
used this methods on many bodies as well as on PCs, labtops, motherboards, amplifiers etc:
Ground your Pentax as well (at the hooks for the belt or with care at the K-mount)
I use this method as well for
cleaning the focusing screen (and the space behind it inside the camera).
Of course the best is to take the screen out of your Pentax.
I hold it with rubber-cloves on both sides (never touch the front-or backside) and into the airstream (without the thin-diameter hose)
Hold tight!
Then turn it and hold it into the airstream as well.
If really dirty I have cleaned focusing screens with very clean (destilled) water, sometimes even with some washing up liquid and then a rinse with water.
Then I dried them the same way with the air suction. It works very well.
*In the past I have worked a lot with electrostatic speakers and electrostatic headphones, their power supplies and particular with direct-coupled amplifiers driving those directly and I have designed active MOS-FET-amplifiers driving subwoofers with the PS for the ELS-Speaker inside that amplifier. We used special connectors but at the beginning had problems that the high-voltage (power was just milli-amperes) arced and damaged the power-MOS-FET's! Of course here we deal with higher voltage but as well with very robust transistors which produced some healthy 160Watts power-output for the subwoofers which were not ESL! The best idea would have been to have the PS separate but the manufacturer of the speakers wanted it otherwise. Hard lesson to learn then.