Pressurization to avoid toxic gas ingress

[nevinjohn]

Contradictory to staircase or liftwell pressurization, what needs to be done to pressurize a room to avoid any toxic gas ingress during an emergency. The bottle neck here is that the fresh air intake is restricted due to the polluted air. Has someone come across the requirement where in air is stored in cylinders or something like that??

Thanks!
Nevin.

[Brian_UK]

Our ex local nuclear control bunker used to have hundreds of oxygen bottles all connected up and ready to go when needed.

You new to considered how long the room will need to be sealed, a recirculating ventilation system with CO² scrubber.

[frank]

Perhaps a VENTILATION FORUM might be able to give some advice??

[install monkey]

http://www.mcaf.co.uk/nuclear.aspx
filtered polluted air

[Brian_UK]

Our ex local nuclear control bunker used to have hundreds of oxygen bottles all connected up and ready to go when needed.

I might add that when the pressure vessel directive came in they dumped all of the oxygen and took the system out of service that they didn't have to be tested.

[Magoo]

Identify the toxic pollutants then add ultra filtration ( HEPA filters ) for the lumps and catalytic convertors specific to toxic content, possibly add ozone generators as a sanitizer. All will not happen with a power supply failure so add a remote generator power supply.

[nevgee]

Petro chem industry used to use an extended fresh air in duct or stack with an inlet that would be 3 to 5 m high, depending on site and hazards. An independant input fan assembly with 100% standy would provide an over pressure of 25 to 50 Pa. All doorways would have air lock arrangement and all penetrations to the builing would be completely sealed and air tight. pressure relief to outside would be via calibrated relief valves / flaps.
Again as Magoo suggests, HEPA filtration or in some cases carbon filters could be used at the fresh air ingress point.

[nevinjohn]

I had suggested the idea of extended fresh air duct, but due to the nature of H2S gas, they are not willing to take the risk, even with chemical filters. Any idea how to pressurize the room considering the door is continously opened? Can I consider the "crack area" as this "door area" in my calculations? I believe this crack method is the only formula that ASHRAE has for pressurization?

[Magoo]

You have to remove the toxic content, otherwise blowing to atmosphere creates a pollution issue for the rest of us mere humans.

[sterl]

Door is continuously open to Outdoors? If its open to an adjacent space you will be pressurizing both spaces. If the pressurization is to be implemented in emergency only, automatic door closer addresses both conditions, maybe....

Is this a "shelter in place" room space? Many of the drilling platforms require such spaces....Lots of architectural detail involved. Check "Red Dog" for the land based units.

[nevinjohn]

You have to remove the toxic content, otherwise blowing to atmosphere creates a pollution issue for the rest of us mere humans.

Yes, we do that with a chemical filter medium. For O&G industry, our concern is with H2S gas, and this is the main reason we are planning to make a Gas Refuge Area, for 1-2hours. (Could help emergency services to arrive in that time frame)

[nevinjohn]

11518

This is the concept. In case of gas leak in the process area, the air lock needs to be pressurized continously even with both the doors opened as personals will be entering the refuge through the air lock. I thought the idea of interlocking the doors, but during an emergency all would be panicking and this would not help.

Inside the refuge, the HVAC system shall run in recirculation mode. All fresh air intake dampers shall be closed in case of gas detection. Only air lock shall take fresh air from process/ambient, treat it in chemical filters and then supplied for required pressurization purpose.

Now, since both doors needs to be considered as "open crack", can I use the ASHRAE orifice equation here as well?

Thanks!
Nevin.

[nevinjohn]

Guys,

I'm still waiting for suggestions. . . . . Anyone?

[RANGER1]

I just looked up "design of toxic refuge" & there seems to be a lot of information.

To me you cannot have doors continuously open.
everyone should be accounted for then keep doors shut.
It talks about being able to withstand a blast, air cylinders to supply air, air monitoring within space &
a flush if air polluted & lots more.

I would say a specialist area of design.

on phone so can't attach links

[nevinjohn]

Yes, unfortunatly these information available limits itself with a portable container. It points to an OEM with compressed air storage and limited to 20-30 people. . .

If the doors are not kept open, do you think the personal on site will "wait" for the air lock doors to get opened? Even with that, there's a chance that the toxic gas would go inside the shelter, and this needs to be avoided at the first place!

[RANGER1]

[QUOTE=nevinjohn;296199]Yes, unfortunatly these information available limits itself with a portable container. It points to an OEM with compressed air storage and limited to 20-30 people. . .

If the doors are not kept open, do you think the personal on site will "wait" for the air lock doors to get opened? Even with that, there's a chance that the toxic gas would go inside the shelter, and this needs to be avoided at the first place![/QUOTE

You may misunderstand room slightly pressurized
but doors open only when people open them momentarily or for a short period
people should only be going in when emergency unless rescue team

[nevinjohn]

Yes, the shelter is planned for 200 personals. Lets say the time required by an individual is approx 3 seconds.
Thefore 200 X 3 = 600 Seconds ; 10 minutes. So this air lock shall maintain 50Pa for 10 min duration considering both the doors opened. Any idea how to do that?