What is Orifice Flange?
What is Orifice Flange?
An orifice flange is a specialized type of flange used in conjunction with an orifice plate to measure the flow rate of liquids, gases, or steam in a pipeline. These flanges are designed to accommodate pressure tapping points, allowing for accurate differential pressure measurement across the orifice plate. Orifice flanges are widely utilized in industries such as oil and gas, chemical processing, water treatment, and power generation.
Types of Orifice Flanges
There are different types of orifice flanges based on their design and application. These include:
Weld Neck Orifice Flange – Provides high strength and is suitable for high-pressure applications.
Slip-On Orifice Flange – Easier to install and is often used in low-pressure systems.
Threaded Orifice Flange – Used in low-pressure applications where welding is not feasible.
Socket Weld Orifice Flange – Suitable for small-diameter pipelines with moderate pressure.
Blind Orifice Flange – Used for testing or temporarily shutting off flow in a pipeline.


Orifice Flange Standards

ASME B16.36 Orifice Flange

ASME B16.5 Orifice Flange

ANSI/ASME B16.47 Orifice Flange

API 6A Orifice Flange
Orifice Flange Dimensions – Class 300 to Class 2500
Class 150 Orifice Flange Dimensions (Weld Neck Raised Face)
Nominal size | O | C | R | X | A | Y | Tg | No. of holes | Diam. of holes | Diam. of bolts | Diam. of bolt circle |
---|---|---|---|---|---|---|---|---|---|---|---|
1″ | 4.88 | 1.5 | 2 | 2.12 | 1.32 | 3.25 | 01/04/07 | 4 | 0.69 | 5/8″ | 3.5 |
124 | 38.1 | 50.8 | 53.8 | 33.5 | 82.6 | 6.4 | 17.5 | 15.9 | 88.9 | ||
1 1/2″ | 6.12 | 1.5 | 2.88 | 2.75 | 1.9 | 3.38 | 01/04/07 | 4 | 0.81 | 3/4″ | 4.5 |
155.4 | 38.1 | 73.2 | 69.9 | 48.3 | 85.9 | 6.4 | 20.6 | 19.1 | 114.3 | ||
2″ | 6.5 | 1.5 | 3.62 | 3.31 | 2.38 | 3.38 | 01/04/07 | 8 | 0.69 | 5/8″ | 5 |
165.1 | 38.1 | 91.9 | 84.1 | 60.5 | 85.9 | 6.4 | 17.5 | 15.9 | 127 | ||
2 1/2″ | 7.5 | 1.5 | 4.12 | 3.94 | 2.88 | 3.5 | 01/04/07 | 8 | 0.81 | 3/4″ | 5.88 |
190.5 | 38.1 | 104.6 | 100.1 | 73.2 | 88.9 | 6.4 | 20.6 | 19.1 | 149.4 | ||
3″ | 8.25 | 1.5 | 5 | 4.62 | 3.5 | 3.5 | 03/08/07 | 8 | 0.81 | 3/4″ | 6.62 |
209.6 | 38.1 | 127 | 117.3 | 88.9 | 88.9 | 9.5 | 20.6 | 19.1 | 168.1 | ||
4″ | 10 | 1.5 | 6.19 | 5.75 | 4.5 | 3.62 | 01/02/07 | 8 | 0.81 | 3/4″ | 7.88 |
254 | 38.1 | 157.2 | 146.1 | 114.3 | 91.9 | 12.7 | 20.6 | 19.1 | 200.2 | ||
6″ | 12.5 | 1.5 | 8.5 | 8.12 | 6.63 | 3.94 | 01/02/07 | 12 | 0.88 | 3/4″ | 10.62 |
317.5 | 38.1 | 215.9 | 206.2 | 168.4 | 100.1 | 12.7 | 22.4 | 19.1 | 269.7 | ||
8″ | 15 | 1.62 | 10.62 | 10.25 | 8.63 | 4.38 | 01/02/07 | 12 | 1 | 7/8″ | 13 |
381 | 41.1 | 269.7 | 260.4 | 219.2 | 111.3 | 12.7 | 25.4 | 22.2 | 330.2 | ||
10″ | 17.5 | 1.88 | 12.75 | 12.62 | 10.75 | 4.62 | 01/02/07 | 16 | 1.12 | 1″ | 15.25 |
444.5 | 47.8 | 323.9 | 320.5 | 273.1 | 117.3 | 12.7 | 28.4 | 25.4 | 387.4 | ||
12″ | 20.5 | 2 | 15 | 14.75 | 12.75 | 5.12 | 01/02/07 | 16 | 1.25 | 1 1/8″ | 17.75 |
520.7 | 50.8 | 381 | 374.7 | 323.9 | 130 | 12.7 | 31.8 | 28.6 | 450.9 | ||
14″ | 23 | 2.12 | 16.25 | 16.75 | 14 | 5.62 | 01/02/07 | 20 | 1.25 | 1 1/8″ | 20.25 |
584.2 | 53.8 | 412.8 | 425.5 | 355.6 | 142.7 | 12.7 | 31.8 | 28.6 | 514.4 | ||
16″ | 25.5 | 2.25 | 18.5 | 19 | 16 | 5.75 | 01/02/07 | 20 | 1.38 | 1 1/4″ | 22.5 |
647.7 | 57.2 | 469.9 | 482.6 | 406.4 | 146.1 | 12.7 | 35.1 | 31.8 | 571.5 | ||
18″ | 28 | 2.38 | 21 | 21 | 18 | 6.25 | 01/02/07 | 24 | 1.38 | 1 1/4″ | 24.75 |
711.2 | 60.5 | 533.4 | 533.4 | 457.2 | 158.8 | 12.7 | 35.1 | 31.8 | 628.7 | ||
20″ | 30.5 | 2.5 | 23 | 23.12 | 20 | 6.38 | 01/02/07 | 24 | 1.38 | 1 1/4″ | 27 |
774.7 | 63.5 | 584.2 | 587.2 | 508 | 162.1 | 12.7 | 35.1 | 31.8 | 685.8 | ||
24″ | 36 | 2.75 | 27.25 | 27.62 | 24 | 6.62 | 01/02/07 | 24 | 1.62 | 1 1/2″ | 32 |
914.4 | 69.9 | 692.2 | 701.5 | 609.6 | 168.1 | 12.7 | 41.1 | 38.1 | 812.8 |
Class 300 Orifice Flange Dimensions (Weld Neck Raised Face)
Size in Inch | Size in mm | Outer Dia. | Flange Thick. | Hub OD | Weld Neck OD | Welding Neck Length | RF Dia. | RF Height | PCD | Orifice Hole dia | No of Bolts | Bolt Size UNC | RF Stud Length | Hole Size | ISO Stud Size | Weight in kg |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A | B | C | D | E | F | G | H | I | ||||||||
1 | 25 | 125 | 36.6 | 54 | 33.4 | 81 | 50.8 | 2 | 88.9 | 6.4 | 4 | 5/8 | 125 | 3/4 | M16 | 4.5 |
1 1/2 | 40 | 155 | 36.6 | 70 | 48.3 | 84 | 73 | 2 | 114.3 | 6.4 | 4 | 3/4 | 135 | 7/8 | M20 | 6.5 |
2 | 50 | 165 | 36.6 | 84 | 60.3 | 84 | 92.1 | 2 | 127 | 6.4 | 8 | 5/8 | 125 | 3/4 | M16 | 7 |
2 1/2 | 65 | 190 | 36.6 | 100 | 73 | 87 | 104.8 | 2 | 149.2 | 6.4 | 8 | 3/4 | 135 | 7/8 | M20 | 7.5 |
3 | 80 | 210 | 36.6 | 117 | 88.9 | 87 | 127 | 2 | 168.3 | 9.5 | 8 | 3/4 | 135 | 7/8 | M20 | 9.4 |
4 | 100 | 255 | 36.6 | 146 | 114.3 | 90 | 157.2 | 2 | 200 | 12.7 | 8 | 3/4 | 135 | 7/8 | M20 | 13.2 |
6 | 150 | 320 | 36.6 | 206 | 168.3 | 98 | 215.9 | 2 | 269.9 | 12.7 | 12 | 3/4 | 135 | 7/8 | M20 | 14.6 |
8 | 200 | 380 | 39.7 | 260 | 219.1 | 110 | 269.9 | 2 | 330.2 | 12.7 | 12 | 7/8 | 145 | 1 | M24 | 30 |
10 | 250 | 445 | 46.1 | 321 | 273 | 116 | 323.8 | 2 | 387.3 | 12.7 | 16 | 1 | 165 | 1 1/8 | M27 | 41 |
12 | 300 | 520 | 49.3 | 375 | 323.8 | 129 | 381 | 2 | 450.8 | 12.7 | 16 | 1 1/8 | 180 | 1 1/4 | M30 | 62 |
14 | 350 | 585 | 52.4 | 425 | 355.6 | 141 | 412.8 | 2 | 514.4 | 12.7 | 20 | 1 1/8 | 185 | 1 1/4 | M30 | 84 |
16 | 400 | 650 | 55.6 | 483 | 406.4 | 144 | 469.9 | 2 | 571.5 | 12.7 | 20 | 1 1/4 | 195 | 1 3/8 | M33 | 111 |
18 | 450 | 710 | 58.8 | 533 | 457 | 157 | 533.4 | 2 | 628.6 | 12.7 | 24 | 1 1/4 | 205 | 1 3/8 | M33 | 138 |
20 | 500 | 775 | 62 | 587 | 508 | 160 | 584.2 | 2 | 685.8 | 12.7 | 24 | 1 1/4 | 215 | 1 3/8 | M33 | 171 |
24 | 600 | 915 | 68.3 | 702 | 610 | 167 | 692.2 | 2 | 812.8 | 12.7 | 24 | 1 1/2 | 240 | 1 5/8 | M39 | 247 |
Class 600 Orifice Flange Dimensions (Weld Neck Raised Face)
Size in Inch | Size in mm | Outer Dia. | Flange Thick. | Hub OD | Weld Neck OD | Welding Neck Length | RF Dia. | RF Height | PCD | Orifice Hole dia | No of Bolts | Bolt Size UNC | RF Stud Length | Hole Size | ISO Stud Size | Weight in kg |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A | B | C | D | E | F | G | H | I | ||||||||
1 | 25 | 125 | 36.6 | 54 | 33.5 | 81 | 50.8 | 7 | 88.9 | 6.4 | 4 | 5/8 | 125 | 3/4 | M16 | 5.5 |
1 1/2 | 40 | 155 | 36.6 | 70 | 48.3 | 84 | 73 | 7 | 114.3 | 6.4 | 4 | 3/4 | 135 | 7/8 | M20 | 7.8 |
2 | 50 | 165 | 36.6 | 84 | 60.3 | 84 | 92.1 | 7 | 127 | 6.4 | 8 | 5/8 | 125 | 3/4 | M16 | 8.3 |
2 1/2 | 65 | 190 | 36.6 | 100 | 73 | 87 | 104.8 | 7 | 149.2 | 6.4 | 8 | 3/4 | 135 | 7/8 | M20 | 10.8 |
3 | 80 | 210 | 36.6 | 117 | 88.9 | 87 | 127 | 7 | 168.3 | 9.5 | 8 | 3/4 | 135 | 7/8 | M20 | 12.6 |
4 | 100 | 275 | 38.1 | 152 | 114.3 | 102 | 157.2 | 7 | 215.9 | 12.7 | 8 | 7/8 | 150 | 1 | M24 | 19 |
6 | 150 | 355 | 47.7 | 222 | 168.3 | 117 | 215.9 | 7 | 292.1 | 12.7 | 12 | 1 | 180 | 1 1/8 | M27 | 37 |
8 | 200 | 420 | 55.6 | 273 | 219.1 | 133 | 269.9 | 7 | 349.2 | 12.7 | 12 | 1 1/8 | 195 | 1 1/4 | M30 | 53 |
10 | 250 | 510 | 63.5 | 343 | 273 | 152 | 323.8 | 7 | 431.8 | 12.7 | 16 | 1 1/4 | 220 | 1 3/8 | M33 | 86 |
12 | 300 | 560 | 66.7 | 400 | 323.8 | 156 | 381 | 7 | 489 | 12.7 | 20 | 1 1/4 | 230 | 1 3/8 | M33 | 102 |
14 | 350 | 605 | 69.9 | 432 | 355.6 | 165 | 412.8 | 7 | 527 | 12.7 | 20 | 1 3/8 | 240 | 1 1/2 | M36 | 150 |
16 | 400 | 685 | 76.2 | 495 | 406.4 | 178 | 469.9 | 7 | 603.2 | 12.7 | 20 | 1 1/2 | 260 | 1 5/8 | M39 | 190 |
18 | 450 | 745 | 82.6 | 546 | 457.2 | 184 | 533.4 | 7 | 654 | 12.7 | 20 | 1 5/8 | 280 | 1 3/4 | M42 | 240 |
20 | 500 | 815 | 88.9 | 610 | 508 | 190 | 584.2 | 7 | 723.9 | 12.7 | 24 | 1 5/8 | 300 | 1 3/4 | M42 | 295 |
24 | 600 | 940 | 101.6 | 718 | 609.6 | 203 | 692.2 | 7 | 838.2 | 12.7 | 24 | 1 7/8 | 335 | 2 | M48 | 365 |
Class 900 Orifice Flange Dimensions (Weld Neck Raised Face)
Size in Inch | Size in mm | Outer Dia. | Flange Thick. | Hub OD | Weld Neck OD | Welding Neck Length | RF Dia. | RF Height | PCD | Orifice Hole dia | No of Bolts | Bolt Size UNC | RF Stud Length | Hole Size | ISO Stud Size | Weight in kg |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A | B | C | D | E | F | G | H | I | ||||||||
1 | 25 | 150 | 38.1 | 52 | 33.5 | 83 | 50.8 | 7 | 101.6 | 6.4 | 4 | 7/8 | 150 | 1 | M24 | 5.4 |
1 1/2 | 40 | 180 | 38.1 | 70 | 48.3 | 89 | 73 | 7 | 123.8 | 6.4 | 4 | 1 | 160 | 1 1/8 | M27 | 7.8 |
2 | 50 | 215 | 38.1 | 105 | 60.3 | 102 | 92.1 | 7 | 165.1 | 6.4 | 8 | 7/8 | 150 | 1 | M30 | 11.5 |
2 1/2 | 65 | 245 | 41.3 | 124 | 73 | 105 | 104.8 | 7 | 190.5 | 6.4 | 8 | 1 | 165 | 1 1/8 | M27 | 15.8 |
3 | 80 | 240 | 38.1 | 127 | 88.9 | 102 | 127 | 7 | 190.5 | 9.5 | 8 | 7/8 | 150 | 1 | M24 | 22 |
4 | 100 | 290 | 44.5 | 159 | 114.3 | 114 | 157.2 | 7 | 235 | 12.7 | 8 | 1 1/8 | 180 | 1 1/4 | M30 | 22 |
6 | 150 | 380 | 55.6 | 235 | 168.3 | 140 | 215.9 | 7 | 317.5 | 12.7 | 12 | 1 1/8 | 195 | 1 1/4 | M30 | 70 |
8 | 200 | 470 | 63.5 | 298 | 219.1 | 162 | 269.9 | 7 | 393.7 | 12.7 | 12 | 1 3/8 | 230 | 1 1/2 | M36 | 119 |
10 | 250 | 545 | 69.9 | 368 | 273 | 184 | 323.8 | 7 | 469.9 | 12.7 | 16 | 1 3/8 | 240 | 1 1/2 | M36 | 204 |
12 | 300 | 610 | 79.4 | 419 | 323.8 | 200 | 381 | 7 | 533.4 | 12.7 | 20 | 1 3/8 | 260 | 1 1/2 | M36 | 303 |
14 | 350 | 640 | 85.8 | 451 | 355.6 | 213 | 412.8 | 7 | 558.8 | 12.7 | 20 | 1 1/2 | 280 | 1 5/8 | M39 | 400 |
16 | 400 | 705 | 88.9 | 508 | 406.4 | 216 | 469.9 | 7 | 616 | 12.7 | 20 | 1 5/8 | 290 | 1 3/4 | M42 | 510 |
18 | 450 | 785 | 101.9 | 565 | 457.2 | 229 | 533.4 | 7 | 685.8 | 12.7 | 20 | 1 7/8 | 330 | 2 | M48 | 738 |
20 | 500 | 855 | 108 | 622 | 508 | 248 | 584.2 | 7 | 749.3 | 12.7 | 20 | 2 | 355 | 2 1/8 | M52 | 932 |
24 | 600 | 1040 | 139.7 | 749 | 609.6 | 292 | 692.2 | 7 | 901.7 | 12.7 | 20 | 2 1/2 | 445 | 2 5/8 | M64 | 1511 |
Class 1500 Orifice Flange Dimensions (Weld Neck Raised Face)
Size in Inch | Size in mm | Outer Dia. | Flange Thick. | Hub OD | Weld Neck OD | Welding Neck Length | RF Dia. | RF Height | PCD | Orifice Hole dia | No of Bolts | Bolt Size UNC | RF Stud Length | Hole Size | ISO Stud Size | Weight in kg |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A | B | C | D | E | F | G | H | I | ||||||||
1 | 25 | 150 | 38.1 | 52 | 33.5 | 83 | 50.8 | 7 | 101.6 | 6.4 | 4 | 7/8 | 150 | 1 | M24 | 5.4 |
1 1/2 | 40 | 180 | 38.1 | 70 | 48.3 | 89 | 73 | 7 | 123.8 | 6.4 | 4 | 1 | 160 | 1 1/8 | M27 | 7.8 |
2 | 50 | 215 | 38.1 | 105 | 60.3 | 102 | 92.1 | 7 | 165.1 | 6.4 | 8 | 7/8 | 150 | 1 | M24 | 11.5 |
2 1/2 | 65 | 245 | 41.3 | 124 | 73 | 105 | 104.8 | 7 | 190.5 | 6.4 | 8 | 1 | 165 | 1 1/8 | M27 | 15.8 |
3 | 80 | 265 | 47.7 | 133 | 88.9 | 117 | 127 | 7 | 203.2 | 9.5 | 8 | 1 1/8 | 185 | 1 1/4 | M30 | 22 |
4 | 100 | 310 | 54 | 162 | 114.3 | 124 | 157.2 | 7 | 241.3 | 12.7 | 8 | 1 1/4 | 205 | 1 3/8 | M33 | 22 |
6 | 150 | 395 | 82.6 | 229 | 168.3 | 171 | 215.9 | 7 | 317.5 | 12.7 | 12 | 1 3/8 | 265 | 1 1/2 | M36 | 70 |
8 | 200 | 485 | 92.1 | 292 | 219.1 | 213 | 269.9 | 7 | 393.7 | 12.7 | 12 | 1 5/8 | 300 | 1 3/4 | M42 | 119 |
10 | 250 | 585 | 108 | 368 | 273 | 254 | 323.8 | 7 | 482.6 | 12.7 | 12 | 1 7/8 | 345 | 1 | M48 | 204 |
12 | 300 | 675 | 123.9 | 451 | 323.8 | 283 | 381 | 7 | 571.5 | 12.7 | 16 | 2 | 380 | 2 1/8 | M52 | 303 |
14 | 350 | 750 | 133.4 | 495 | 355.6 | 298 | 412.8 | 7 | 635 | 12.7 | 16 | 2 1/4 | 415 | 2 3/8 | M56 | 400 |
16 | 400 | 825 | 146.1 | 552 | 406.4 | 311 | 469.9 | 7 | 704.8 | 12.7 | 16 | 2 1/2 | 450 | 2 5/8 | M64 | 510 |
18 | 450 | 915 | 162 | 597 | 457.2 | 327 | 533.4 | 7 | 774.7 | 12.7 | 16 | 2 3/4 | 500 | 2 7/8 | M72 | 738 |
20 | 500 | 985 | 177.8 | 641 | 508 | 356 | 584.2 | 7 | 831.8 | 12.7 | 16 | 3 | 545 | 3 1/8 | M76 | 932 |
24 | 600 | 1170 | 203.2 | 762 | 609.6 | 406 | 692.2 | 7 | 990.6 | 12.7 | 16 | 3 1/2 | 620 | 3 5/8 | M90 | 1511 |
Class 2500 Orifice Flange Dimensions (Weld Neck Raised Face)
Size in Inch | Size in mm | Outer Dia. | Flange Thick. | Hub OD | Weld Neck OD | Welding Neck Length | RF Dia. | RF Height | PCD | Orifice Hole dia | No of Bolts | Bolt Size UNC | RF Stud Length | Hole Size | ISO Stud Size | Weight in kg |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A | B | C | D | E | F | G | H | I | ||||||||
1 | 25 | 160 | 38.1 | 57 | 33.5 | 92 | 50.8 | 7 | 108 | 6.4 | 4 | 7/8 | 150 | 1 | M24 | 6.5 |
1 1/2 | 40 | 205 | 44.5 | 79 | 48.3 | 111 | 73 | 7 | 146 | 6.4 | 4 | 1 1/8 | 180 | 1 1/4 | M30 | 13 |
2 | 50 | 235 | 50.8 | 95 | 60.3 | 127 | 92.1 | 7 | 171.4 | 6.4 | 8 | 1 | 185 | 1 1/8 | M27 | 19 |
2 1/2 | 65 | 265 | 57.2 | 114 | 73 | 143 | 104.8 | 7 | 196.8 | 6.4 | 8 | 1 1/8 | 205 | 1 1/4 | M30 | 24 |
3 | 80 | 305 | 66.7 | 133 | 88.9 | 168 | 127 | 7 | 228.6 | 9.5 | 8 | 1 1/4 | 230 | 1 3/8 | M33 | 43 |
4 | 100 | 355 | 76.2 | 165 | 114.3 | 190 | 157.2 | 7 | 273 | 12.7 | 8 | 1 1/2 | 260 | 1 5/8 | M39 | 66 |
6 | 150 | 485 | 108 | 235 | 168.3 | 273 | 215.9 | 7 | 368.3 | 12.7 | 8 | 2 | 350 | 2 1/8 | M52 | 172 |
8 | 200 | 550 | 127 | 305 | 219.1 | 318 | 269.9 | 7 | 438.2 | 12.7 | 12 | 2 | 385 | 2 1/8 | M52 | 261 |
10 | 250 | 675 | 165.1 | 375 | 273 | 419 | 323.8 | 7 | 539.8 | 12.7 | 12 | 2 1/2 | 490 | 2 5/8 | M64 | 485 |
12 | 300 | 760 | 184.2 | 441 | 323.8 | 464 | 381 | 7 | 619.1 | 12.7 | 12 | 2 3/4 | 540 | 2 7/8 | M72 | 730 |
Material
- Carbon Steel (ASTM A105, A350 LF2) – Ideal for moderate pressure and temperature conditions.
- Stainless Steel (ASTM A182 F304, F316, F321) – Provides excellent corrosion resistance.
- Alloy Steel (ASTM A182 F11, F22, F91) – Used in high-temperature and high-pressure environments.
- Duplex & Super Duplex Stainless Steel – Offers superior corrosion resistance in aggressive environments.
- Nickel Alloys (Inconel, Hastelloy, Monel) – Used in extreme conditions such as chemical processing.
Pressure Ratings of Orifice Flanges
- Class 150 – Suitable for low-pressure applications.
- Class 300 – Used in medium-pressure systems.
- Class 600 – Common in higher pressure environments.
- Class 900 – For high-pressure systems.
- Class 1500 & 2500 – Used in extremely high-pressure applications.
Components of an Orifice Flange Assembly
Orifice Flanges – The main flanges that hold the orifice plate in place.
Orifice Plate – A plate with a precisely machined hole that creates a pressure differential.
Gaskets – Ensures a leak-proof seal between the flanges and the orifice plate.
Stud Bolts & Nuts – Secure the flanges together.
Jack Screws – Help in easy removal of the orifice plate.
Tapping Points – Allow for pressure measurement.
Advantages
- Accurate Flow Measurement – Ensures reliable readings in industrial applications.
- Cost-Effective – More economical compared to other flow measuring devices.
- Durability – Manufactured from robust materials to withstand harsh conditions.
- Ease of Installation – Simple to integrate into existing pipeline systems.
- Standardization – Available in multiple standard sizes and pressure ratings.
Application
- Oil & Gas – Flow monitoring in pipelines and refineries.
- Chemical Processing – Accurate measurement of chemical flows.
- Water Treatment Plants – Monitoring water distribution and treatment processes.
- Power Plants – Measuring steam and fluid flow.
- HVAC Systems – Ensuring proper flow of air and gases.