How to Calc "In-Use" System That Spans MAQs?

2/2/2023

We have a situation where we'll have a piece of equipment in one control area that has a closed-use pipe arrangement with oxidizing gases that goes through different control areas. I've gotten conflicting feedback on this.

How do you figure the amount of "in-use" for each control area?

Here's a sketch of the concept:

The equipment that is using the oxygen is on the fourth floor Control Area 2. The tanks that feed it are (2) 200 CF oxygen tanks that are in the second floor Control Area 1.

Which of the following two scenarios is the proper way to tally up the "in-use" quantity for the fourth floor Control Area 2 when comparing against the Maximum Allowable Quantities (MAQs)?

Concept #1: The "in-use" amount is only the gas within the equipment itself, and only the gas within the piping to the extent of the control area wall.
Concept #2: The "in-use" amount is all of the gas within the equipment itself, and all of the gas within all of the piping, and all of the gas within the (2) oxygen tanks which are actively hooked up to it.

My initial gut reaction was that the second option is correct, but now I’m not sure. My reasoning being that if there is an event in 4th floor control area 2 that causes a leak or something like that, it’s not going to just leak out what is physically within the control area… it’s going to leak out everything in all of the piping, all of the equipment, and all of the hooked up tanks. This is all presuming there are no safety devices to stop this from happening.

Assuming my initial gut reaction was correct, is there a way to limit the amount so that it stops at the control area wall?

As in: is there a safety device such as an automatic shutoff valve we can put at the wall such that in the event of a leak or other event, the automatic valve will shut off and then we only have to count the amount of gas between the equipment and the shutoff valve?

I’ve looked in the IBC and its commentary for more info, but couldn’t find anything helpful. I’ve also reached out to a number of different people and there seems to be a variety of different opinions on it.

Thanks in advance.

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12 Comments

Chad

2/2/2023 08:22:02 am

#2

In use is not in storage.

If its connected to utilization equipment, it is in use.

chad

2/2/2023 08:24:52 am

IMO, this applies and that fits in use.

2016 NFPA 400

3.3.86* Use. To place a material, including solids, liquids,
and gases, into action.

3.3.86.1* Closed System Use. Use of a solid or liquid hazardous material in a closed vessel or system that remains closed during normal operations where vapors emitted by the
product are not liberated outside of the vessel or system
and the product is not exposed to the atmosphere during
normal operations and all uses of compressed gases.
3.3.86.2* Open System Use. Use of a solid or liquid hazardous
material in a vessel or system that is continuously open
to the atmosphere during normal operations and where
vapors are liberated or the product is exposed to the atmosphere during normal operations.

Mike

2/2/2023 01:04:47 pm

This will only apply if NFPA 400 is the charging document within the project jurisdiction. In jurisdictions that use IBC, NFPA 400 is not a referenced standard and is therefore not enforceable. IFC does reference NFPA 400, but not for defining in-use systems. It does reference it for quantities of oxidizing liquids and solids, but not gases.

In a case where IBC/IFC is the charging document, we would need to turn to those documents for the definitions of various in-use systems (both open and closed use), as well as the MAQ of these types of oxidizing gases.

2/2/2023 01:00:46 pm

According to IBC/IFC, though... in-use DOES count towards storage. Sub-Note B applies:

"The aggregate quantity in use and storage shall not exceed the quantity specified for storage."

Also, the commentary for Closed in-use piping systems note that all equipment within the continuous system is to be accounted for, including the equipment, the piping, and the storage vessels. Typically, all of the above is included within a single control area, so it's easy to figure out... but in this case it traverses multiple control areas. So which control area to apply it to?

The most conservative approach would be that the full quantity of the in-use system applies to each/every control area that the system passes through.

The least conservative approach would be that each control area only needs to consider the piping/equipment/vessels which are physically contained within that control area.

2/2/2023 01:10:10 pm

Apologies, I just re-read your original comment and see that you are saying the same thing: the whole thing is considered in-use.. everything hooked up to the system is in-use.

I agree. Sorry for the confusion.

Glenn Berger

2/2/2023 09:01:35 am

This question would be best answered by someone specializing in health care / hospital design.

I would add that y0our situation all the O2 would be considered in-use. Depending on the equipment would determine the it would be open or closed-use.

2/2/2023 12:45:47 pm

Glenn,
It's important to note that the ICC characterizes all gas usage as "closed", since it is not possible to have an open-use gas arrangement as it would dissipate into the air.

I agree that all O2 would be considered in-use... but which control area does it apply to? You could make the same argument for literally any control area that it passes through: if there is a leak, all of the O2 is going to come out at the point of the leak, not just what is bounded by the control area walls.

Todd E Wyatt

2/2/2023 09:02:23 am

Oxygen is a “Class 2 Oxidizer.”

Per 2021 IBC Table 307.1(1), in a gas form, the MAQ for Oxidizers for Storage and for Use-Closed Systems is “NA”.
In a liquid state, an “Oxidizer Class 2” is limited to MAQ of 250 lbs for Storage and for Use-Closed Systems. If the building is sprinklered, MAQs are increased by 100%.
Per 2021 IBC Table 414.2.5(1), “oxidizers” are limited to MAQs according to their “Class” ... 1, 2, 3, or 4 ... in Group M and S occupancies.

2021 IFC Chapter 63 Oxidizers, Oxidizing Gases and Oxidizing Cryogenic Fluids includes the following “shutoff” requirements :

Section 6303 General Requirements
6303.1 Quantities Not Exceeding the Maximum Allowable Quantity Per Control Area
The storage and use of oxidizing materials in amounts not exceeding the maximum allowable quantity per control area indicated in Section 5003.1 shall be in accordance with Sections 5001, 5003, 6301 and 6303. Oxidizing gases shall also comply with Chapter 53.
6303.1.1 Special Limitations for Indoor Storage and Use by Occupancy
The indoor storage and use of oxidizing materials shall be in accordance with Sections 6303.1.1.1 through 6303.1.1.2.
6303.1.2 Emergency Shutoff
Compressed gas systems conveying oxidizing gases shall be provided with approved manual or automatic emergency shutoff valves that can be activated at each point of use and at each source.
6303.1.2.1 Shutoff at Source
A manual or automatic fail-safe emergency shutoff valve shall be installed on supply piping at the cylinder or bulk source. Manual or automatic cylinder valves are allowed to be used as the required emergency shutoff valve where the source of supply is limited to unmanifolded cylinder sources.
6303.1.2.2 Shutoff at Point of Use
A manual or automatic emergency shutoff valve shall be installed on the supply piping at the point of use or at a point where the equipment using the gas is connected to the supply system.

This would address your concern regarding an “... event in 4th floor control area 2 that causes a leak ...”.

2/2/2023 12:54:51 pm

Todd,
It's important to note that Oxygen in the context of this table is an "Oxidizing Gas" in gaseous form. That is why it is listed as "N/A" within the "Oxidizer" row. The "Oxidizer" row only applies to liquid and solid oxidizers. The separate "Oxidizing Gas" row applies to oxidizing gases (in gaseous and liquid forms) as its name implies. 1500 cubic feet, which can be doubled for a fully sprinklered building, and doubled again for a gas room/cabinets. However on the 4th floor of a building, control area MAQs are greatly reduced to only 12.5% of the full quantity. So in a fully sprinklered building without gas cabinets, on the 4th floor you'd be limited to 375 cubic feet of oxidizing gas:
(1500 CF * 2)*12.5%=375 CF.

The information regarding the emergency shutoffs is helpful, and reconciles the concept of only counting the in-use gas within the boundaries of the control area, since the safety devices will prevent an unmitigated event that involves all gas within the closed use system.

Alex

2/2/2023 11:45:43 am

Hi,

I've run into issues like this before in the past where compressed gas cylinders are stored outdoors and piped inside. For me, during my review, the gases have been inert with no limit regarding the MAQ.

For you, oxidizing gas is limited to 1,500 CF (in an unsprinklered building), 1st floor. Therefore your limits are:
Second Floor CA1: 750 CF
Fourth Floor CA2: 187.5 CF

Even with a sprinklered building, if you were to assume all 400 CF in use on the fourth floor, you would be over your MAQ (375CF).

I'm not aware of a device/solenoid that would allow you to only calculate the quantity of O2 that is truly in your 4th floor CA. I would research emergency solenoid valves and talk to a few reps to see if there is something out there for this case. Would love an update down the road on this!

Alex

2/2/2023 11:48:13 am

Agreed, no device would alleviate. Most places limit themselves to the 375 CF to avoid CA's

Tom

2/15/2023 08:42:50 am

NFPA 99 covers this I believe. Sorry not in a place I can research/reference it

How to Calc "In-Use" System That Spans MAQs?

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