TSS USA conduit and cable pathway installation

Fire Sleeve Fill Calculator

Built for Firestop Contractors

Standard conduit fill math doesn't apply to fire-rated sleeves. Each Hilti® and STI® device has a UL system number that dictates exactly how many cables of each type are allowed. This calculator pulls from manufacturer-published test data so you get the actual listed capacity, not a percentage guess. We built it because we got tired of flipping through 40-page UL detail sheets on job sites.

Switch calculator

General EMT PVC Cat6 / Data Low VoltageFire Sleeves

Estimates based on NEC, NFPA, and IEEE standards. For reference only. Consult a licensed professional for critical design decisions.

Sleeve and Conduit Fill Tool

Free, NEC-compliant conduit fill calculator for electricians, low-voltage technicians, estimators, and engineers. Determine how many wires or cables safely fit inside various conduit types.

Conduit / Sleeve Type

Device Size

Cable 1

Industry

Cable Type

Quantity

⚡

Select your conduit and cables, then click Calculate

Quick Reference

Low Voltage Conduit Fill Chart

Maximum cable count per conduit size at 40% fill — computed from manufacturer cable OD data and NEC Chapter 9 formulas.

Cable	OD	1/2"	3/4"	1"	1-1/4"	1-1/2"	2"	2-1/2"	3"	3-1/2"	4"
Ethernet
Cat5e UTP	0.196"	4	7	11	19	26	44	77	117	153	195
Cat5e STP	0.225"	3	5	8	15	20	33	58	88	116	148
Cat6 UTP	0.24"	2	4	7	13	18	29	51	78	102	130
Cat6 STP	0.273"	2	3	5	10	13	22	40	60	78	100
Cat6a UTP	0.3"	1	3	4	8	11	18	33	50	65	83
Cat6a STP	0.276"	2	3	5	9	13	22	39	59	77	98
Cat8 S/FTP	0.335"	1	2	3	6	9	15	26	40	52	66
Fire Wire / Multi Conductor
14/2	0.201"	3	6	10	18	25	42	73	111	145	185
14/4	0.236"	2	4	7	13	18	30	53	80	105	134
16/2	0.166"	5	9	15	27	37	62	108	163	213	272
16/4	0.191"	4	7	12	20	28	46	81	123	161	205
18/2	0.151"	6	11	19	33	45	74	130	197	257	329
18/4	0.166"	5	9	15	27	37	62	108	163	213	272
22/2	0.132"	8	15	25	43	59	98	171	258	337	431
22/4	0.14"	7	13	22	38	52	87	152	229	299	383
22/6	0.178"	4	8	13	24	32	53	94	142	185	237
Access Control Cable
Composite Cable	0.415"	—	1	2	4	6	9	17	26	34	43
Shielded Composite	0.463"	—	1	2	3	4	7	13	21	27	35
18/4 Multi-Conductor	0.166"	5	9	15	27	37	62	108	163	213	272
18/2 Multi-Conductor	0.151"	6	11	19	33	45	74	130	197	257	329
22/2 Multi-Conductor	0.132"	8	15	25	43	59	98	171	258	337	431
22/4 Multi-Conductor	0.14"	7	13	22	38	52	87	152	229	299	383
22/6 Shielded	0.178"	4	8	13	24	32	53	94	142	185	237
Fiber (Aluminum Interlock)
6 strand	0.504"	—	1	1	2	4	6	11	17	23	29
12 strand	0.555"	—	—	1	2	3	5	9	14	19	24
24 strand	0.606"	—	—	1	2	2	4	8	12	16	20
48 strand	0.906"	—	—	—	—	1	2	3	5	7	9
72 strand	1"	—	—	—	—	1	1	2	4	5	7
Fiber (Un Armored tight buffer)
6 strand	0.2"	3	6	11	19	25	42	74	112	146	187
12 strand	0.24"	2	4	7	13	18	29	51	78	102	130
24 strand	0.31"	1	2	4	7	10	17	31	46	61	78
48 strand	0.66"	—	—	1	1	2	3	6	10	13	17
72 strand	0.79"	—	—	—	1	1	2	4	7	9	12
Fiber (Un Armored loose buffer)
6 strand	0.2"	3	6	11	19	25	42	74	112	146	187
12 strand	0.2"	3	6	11	19	25	42	74	112	146	187
24 strand	0.32"	1	2	4	7	10	16	29	43	57	73
48 strand	0.32"	1	2	4	7	10	16	29	43	57	73
72 strand	0.42"	—	1	2	4	5	9	16	25	33	42

Computed using NEC Chapter 9 area-based formula at 40% fill with manufacturer-published cable outside diameters. Values are for 3+ cables of the same type. Showing EMT conduit.

Cable	OD	1/2"	3/4"	1"	1-1/4"	1-1/2"	2"	2-1/2"	3"	3-1/2"	4"
Ethernet
Cat5e UTP	0.196"	4	7	11	19	26	44	77	117	153	195
Cat5e STP	0.225"	3	5	8	15	20	33	58	88	116	148
Cat6 UTP	0.24"	2	4	7	13	18	29	51	78	102	130
Cat6 STP	0.273"	2	3	5	10	13	22	40	60	78	100
Cat6a UTP	0.3"	1	3	4	8	11	18	33	50	65	83
Cat6a STP	0.276"	2	3	5	9	13	22	39	59	77	98
Cat8 S/FTP	0.335"	1	2	3	6	9	15	26	40	52	66
Fire Wire / Multi Conductor
14/2	0.201"	3	6	10	18	25	42	73	111	145	185
14/4	0.236"	2	4	7	13	18	30	53	80	105	134
16/2	0.166"	5	9	15	27	37	62	108	163	213	272
16/4	0.191"	4	7	12	20	28	46	81	123	161	205
18/2	0.151"	6	11	19	33	45	74	130	197	257	329
18/4	0.166"	5	9	15	27	37	62	108	163	213	272
22/2	0.132"	8	15	25	43	59	98	171	258	337	431
22/4	0.14"	7	13	22	38	52	87	152	229	299	383
22/6	0.178"	4	8	13	24	32	53	94	142	185	237
Access Control Cable
Composite Cable	0.415"	—	1	2	4	6	9	17	26	34	43
Shielded Composite	0.463"	—	1	2	3	4	7	13	21	27	35
18/4 Multi-Conductor	0.166"	5	9	15	27	37	62	108	163	213	272
18/2 Multi-Conductor	0.151"	6	11	19	33	45	74	130	197	257	329
22/2 Multi-Conductor	0.132"	8	15	25	43	59	98	171	258	337	431
22/4 Multi-Conductor	0.14"	7	13	22	38	52	87	152	229	299	383
22/6 Shielded	0.178"	4	8	13	24	32	53	94	142	185	237
Fiber (Aluminum Interlock)
6 strand	0.504"	—	1	1	2	4	6	11	17	23	29
12 strand	0.555"	—	—	1	2	3	5	9	14	19	24
24 strand	0.606"	—	—	1	2	2	4	8	12	16	20
48 strand	0.906"	—	—	—	—	1	2	3	5	7	9
72 strand	1"	—	—	—	—	1	1	2	4	5	7
Fiber (Un Armored tight buffer)
6 strand	0.2"	3	6	11	19	25	42	74	112	146	187
12 strand	0.24"	2	4	7	13	18	29	51	78	102	130
24 strand	0.31"	1	2	4	7	10	17	31	46	61	78
48 strand	0.66"	—	—	1	1	2	3	6	10	13	17
72 strand	0.79"	—	—	—	1	1	2	4	7	9	12
Fiber (Un Armored loose buffer)
6 strand	0.2"	3	6	11	19	25	42	74	112	146	187
12 strand	0.2"	3	6	11	19	25	42	74	112	146	187
24 strand	0.32"	1	2	4	7	10	16	29	43	57	73
48 strand	0.32"	1	2	4	7	10	16	29	43	57	73
72 strand	0.42"	—	1	2	4	5	9	16	25	33	42

Computed using NEC Chapter 9 area-based formula at 40% fill with manufacturer-published cable outside diameters. Values are for 3+ cables of the same type. Showing RMC conduit.

Cable	OD	1/2"	3/4"	1"	1-1/4"	1-1/2"	2"	2-1/2"	3"	3-1/2"	4"
Ethernet
Cat5e UTP	0.196"	4	7	11	19	26	44	63	98	131	168
Cat5e STP	0.225"	3	5	8	15	20	33	48	74	99	128
Cat6 UTP	0.24"	2	4	7	13	18	29	42	65	87	112
Cat6 STP	0.273"	2	3	5	10	13	22	32	50	67	86
Cat6a UTP	0.3"	1	3	4	8	11	18	27	41	55	72
Cat6a STP	0.276"	2	3	5	9	13	22	32	49	66	85
Cat8 S/FTP	0.335"	1	2	3	6	9	15	21	33	44	57
Fire Wire / Multi Conductor
14/2	0.201"	3	6	10	18	25	42	60	93	124	160
14/4	0.236"	2	4	7	13	18	30	43	67	90	116
16/2	0.166"	5	9	15	27	37	62	88	136	182	235
16/4	0.191"	4	7	12	20	28	46	66	103	138	177
18/2	0.151"	6	11	19	33	45	74	106	165	220	284
18/4	0.166"	5	9	15	27	37	62	88	136	182	235
22/2	0.132"	8	15	25	43	59	98	139	216	288	372
22/4	0.14"	7	13	22	38	52	87	124	192	256	330
22/6	0.178"	4	8	13	24	32	53	76	118	158	204
Access Control Cable
Composite Cable	0.415"	—	1	2	4	6	9	14	21	29	37
Shielded Composite	0.463"	—	1	2	3	4	7	11	17	23	30
18/4 Multi-Conductor	0.166"	5	9	15	27	37	62	88	136	182	235
18/2 Multi-Conductor	0.151"	6	11	19	33	45	74	106	165	220	284
22/2 Multi-Conductor	0.132"	8	15	25	43	59	98	139	216	288	372
22/4 Multi-Conductor	0.14"	7	13	22	38	52	87	124	192	256	330
22/6 Shielded	0.178"	4	8	13	24	32	53	76	118	158	204
Fiber (Aluminum Interlock)
6 strand	0.504"	—	1	1	2	4	6	9	14	19	25
12 strand	0.555"	—	—	1	2	3	5	7	12	16	21
24 strand	0.606"	—	—	1	2	2	4	6	10	13	17
48 strand	0.906"	—	—	—	—	1	2	2	4	6	7
72 strand	1"	—	—	—	—	1	1	2	3	5	6
Fiber (Un Armored tight buffer)
6 strand	0.2"	3	6	11	19	25	42	60	94	125	162
12 strand	0.24"	2	4	7	13	18	29	42	65	87	112
24 strand	0.31"	1	2	4	7	10	17	25	39	52	67
48 strand	0.66"	—	—	1	1	2	3	5	8	11	14
72 strand	0.79"	—	—	—	1	1	2	3	6	8	10
Fiber (Un Armored loose buffer)
6 strand	0.2"	3	6	11	19	25	42	60	94	125	162
12 strand	0.2"	3	6	11	19	25	42	60	94	125	162
24 strand	0.32"	1	2	4	7	10	16	23	36	49	63
48 strand	0.32"	1	2	4	7	10	16	23	36	49	63
72 strand	0.42"	—	1	2	4	5	9	13	21	28	36

Computed using NEC Chapter 9 area-based formula at 40% fill with manufacturer-published cable outside diameters. Values are for 3+ cables of the same type. Showing PVC Sch40 conduit.

Cable	OD	1/2"	3/4"	1"	1-1/4"	1-1/2"	2"	2-1/2"	3"	3-1/2"	4"
Ethernet
Cat5e UTP	0.196"	3	5	9	17	23	39	56	87	117	152
Cat5e STP	0.225"	2	4	7	12	17	29	42	66	89	115
Cat6 UTP	0.24"	2	3	6	11	15	26	37	58	78	101
Cat6 STP	0.273"	1	2	4	8	12	20	28	45	60	78
Cat6a UTP	0.3"	1	2	4	7	10	16	23	37	50	65
Cat6a STP	0.276"	1	2	4	8	11	19	28	44	59	76
Cat8 S/FTP	0.335"	1	1	3	5	8	13	19	29	40	52
Fire Wire / Multi Conductor
14/2	0.201"	2	5	9	16	22	37	53	83	112	144
14/4	0.236"	2	3	6	11	16	27	38	60	81	105
16/2	0.166"	4	7	13	23	32	54	78	122	164	212
16/4	0.191"	3	6	10	17	24	41	59	92	124	160
18/2	0.151"	5	9	16	28	39	65	94	147	198	256
18/4	0.166"	4	7	13	23	32	54	78	122	164	212
22/2	0.132"	6	12	21	37	51	86	123	193	259	336
22/4	0.14"	6	11	18	33	45	76	110	171	230	298
22/6	0.178"	3	6	11	20	28	47	68	106	142	184
Access Control Cable
Composite Cable	0.415"	—	1	2	3	5	8	12	19	26	33
Shielded Composite	0.463"	—	1	1	3	4	7	10	15	21	27
18/4 Multi-Conductor	0.166"	4	7	13	23	32	54	78	122	164	212
18/2 Multi-Conductor	0.151"	5	9	16	28	39	65	94	147	198	256
22/2 Multi-Conductor	0.132"	6	12	21	37	51	86	123	193	259	336
22/4 Multi-Conductor	0.14"	6	11	18	33	45	76	110	171	230	298
22/6 Shielded	0.178"	3	6	11	20	28	47	68	106	142	184
Fiber (Aluminum Interlock)
6 strand	0.504"	—	—	1	2	3	5	8	13	17	23
12 strand	0.555"	—	—	1	2	2	4	7	10	14	19
24 strand	0.606"	—	—	—	1	2	4	5	9	12	15
48 strand	0.906"	—	—	—	—	1	1	2	4	5	7
72 strand	1"	—	—	—	—	—	1	2	3	4	5
Fiber (Un Armored tight buffer)
6 strand	0.2"	2	5	9	16	22	37	53	84	113	146
12 strand	0.24"	2	3	6	11	15	26	37	58	78	101
24 strand	0.31"	1	2	3	6	9	15	22	35	47	60
48 strand	0.66"	—	—	—	1	2	3	4	7	10	13
72 strand	0.79"	—	—	—	1	1	2	3	5	7	9
Fiber (Un Armored loose buffer)
6 strand	0.2"	2	5	9	16	22	37	53	84	113	146
12 strand	0.2"	2	5	9	16	22	37	53	84	113	146
24 strand	0.32"	1	2	3	6	8	14	21	32	44	57
48 strand	0.32"	1	2	3	6	8	14	21	32	44	57
72 strand	0.42"	—	1	2	3	5	8	12	19	25	33

Computed using NEC Chapter 9 area-based formula at 40% fill with manufacturer-published cable outside diameters. Values are for 3+ cables of the same type. Showing PVC Sch80 conduit.

Fire-Rated Reference

Fire-Rated Sleeve Fill Chart

Maximum cable count per fire-rated sleeve by cable outside diameter. These are UL-tested manufacturer values — not NEC area calculations.

Cable OD	EZD22	EZD33	EZD44+
0.118"22/2	80	352	868
0.138"22/4	63	266	648
0.157"18/2	42	192	483
0.177"18/4	35	154	378
0.197"Cat5e UTP	30	130	304
0.217"8 AWG THHN	20	108	255
0.236"Cat6 UTP	20	88	210
0.256"6 AWG THHN	12	70	168
0.276"Cat6a STP	12	63	156
0.315"Cat6a UTP	9	48	110
0.354"Cat8	6	35	90
0.394"Composite	6	30	72
0.433"Shielded Comp.	4	24	56
0.492"6-str Armor Fiber	4	20	42
0.591"12-str Armor Fiber	2	12	30
0.709"24-str Armor Fiber	1	6	20
0.787"48-str Armor Fiber	1	6	16
0.984"48-str Armor Fiber	1	4	9
1.181"72-str Armor Fiber	—	2	6
1.378"1000 kcmil	—	1	4

Source: STI EZPath cable transit data. EZD22/EZD33/EZD44+ device sizes. UL tested values.

Cable OD	Speed 2"	Speed 4"	Modular S	Modular M	Modular L
0.118"22/2	163	819	180	486	1188
0.138"22/4	121	596	144	368	851
0.157"18/2	88	451	112	280	660
0.177"18/4	69	356	84	216	522
0.197"Cat5e UTP	56	287	66	176	416
0.216"8 AWG THHN	45	240	50	150	360
0.236"Cat6 UTP	37	199	45	117	286
0.256"6 AWG THHN	32	164	32	96	240
0.275"Cat6a STP	27	141	28	88	198
0.314"Cat6a UTP	19	109	28	70	160
0.354"Cat8	16	85	18	54	126
0.394"Composite	13	61	15	40	104
0.433"Shielded Comp.	11	50	10	35	84
0.491"6-str Armor Fiber	7	38	8	24	60
0.59"12-str Armor Fiber	5	26	6	15	40
0.708"24-str Armor Fiber	3	19	3	12	28
0.786"48-str Armor Fiber	2	14	2	8	24
0.983"48-str Armor Fiber	1	8	2	6	15
1.179"72-str Armor Fiber	1	7	1	2	8
1.375"1000 kcmil	1	3	—	2	6

Source: Hilti published cable capacity data. Speed Sleeve (2"/4") and Modular Sleeve (S/M/L) sizes. Manufacturer tested values.

Reference

Fire-Rated Sleeve Devices

Capacities per manufacturer UL testing

UL-Tested

Hilti Speed Sleeve

CP 653 — 2" and 4" round sleeves. Intumescent insert expands under heat to seal the penetration. Best for round core-drilled holes with moderate cable counts.

UL-Tested

Hilti Modular Sleeve

CFS-MSL — Small (2.4" ID), Medium (4.1" ID), Large (5.7" ID). Stackable modular blocks with individual cable channels. Ideal for high-density pathway walls.

UL-Tested

STI EZ Path

EZD22 (2-gang), EZD33 (3-gang), EZD44+ (4-gang). Rectangular fire-rated device with removable pads. Re-enterable without breaking the fire seal.

Mfr-Rated

Fill Method

Fire-rated sleeves use manufacturer-tested cable capacities, not NEC percentage fill. Each device is UL-listed with a specific system number that dictates maximum cable count by type and OD.

Contractor Reference

Fire-Rated Sleeve Guide

Everything you need to know about fire sleeve fill, UL system numbers, and passing fire marshal inspections on the first walk-through.

What Fire-Rated Sleeves Are and When Code Requires Them

Every commercial building has fire-rated walls and floors designed to contain fire for a specific duration, typically 1 or 2 hours. The moment you drill a hole through one of those barriers to run cable, you destroy the fire rating. Fire-rated sleeves restore that rating by providing a tested, listed pathway that maintains the barrier's integrity during a fire. Building codes (IBC Section 714, NFPA 101) require that every penetration through a fire-rated assembly be firestopped with a system that matches or exceeds the barrier's rating. This isn't optional.

An unrated penetration in a 2-hour corridor wall means the entire wall assembly fails inspection. Each sleeve device carries a UL system number (like W-L-7079 for Hilti® or CAJ1074 for STI®) that specifies exactly which cables, how many, and what sealant to use. Deviate from that system and the listing is void, even if the sleeve is physically installed.

Hilti Speed Sleeve vs Hilti Modular Sleeve vs STI EZ Path

These three products solve the same problem differently, and picking the wrong one costs you time and money. Hilti® CP 653 Speed Sleeves come in 2" and 4" round sizes. They're fast to install in core-drilled holes and work well for small to moderate cable bundles. The intumescent material inside expands at roughly 300°F to seal the opening. Downside: once filled, adding cables later means breaking the seal. Hilti® CFS-MSL Modular Sleeves use a block-and-frame system in Small (2.4" ID), Medium (4.1" ID), and Large (5.7" ID) configurations.

Individual cable channels make them ideal for high-density telecom rooms where you might have 50+ cables through a single wall. They're more expensive per opening but the modular design pays off when cable counts are high. STI® EZ Path® devices (EZD22, EZD33, EZD44+) use a rectangular gang-box form factor with removable intumescent pads. The big advantage: they're fully re-enterable. Pull a pad, add cables, replace the pad. For buildings with frequent tenant changes or ongoing IT upgrades, EZ Path® devices save significant labor on return trips.

The EZD44+ four-gang device handles the most cable of any single device in this category.

Why Fire Sleeve Fill Differs from NEC Conduit Fill

Contractors who treat fire-rated sleeves like conduit get burned on inspections. NEC Chapter 9 uses percentage-based fill (40% for 3+ conductors) calculated from the conduit's internal cross-sectional area. Fire-rated sleeves don't work that way. Each device is tested by UL with specific cable types and quantities. The intumescent material inside needs air space to expand properly during a fire. Overfill the sleeve and the intumescent can't fully expand, which means the seal fails under fire conditions even though it looked fine during installation.

A 4" Hilti® Speed Sleeve might physically fit 30 Cat6a cables, but the UL listing might cap it at 19. That's not a suggestion. The manufacturer ran fire tests at that specific fill level and proved the seal holds for 2 hours. Go beyond the tested quantity and you're installing an unlisted assembly. This calculator uses manufacturer-published cable capacities rather than NEC area calculations, giving you the actual tested limit for each device.

Installation Mistakes That Void the UL Listing

We see the same five mistakes on job sites repeatedly, and every one of them voids the firestop listing. First: overfilling. Cramming extra cables past the manufacturer's tested capacity turns a listed assembly into a code violation. Second: wrong sealant. Each UL system number specifies a particular firestop sealant (like Hilti® CFS-S SIL or STI® SpecSeal). Substituting a different brand or product invalidates the system, even if it's also a fire-rated sealant. Third: mixing listed and unlisted components.

You can't put a generic foam plug next to a listed sleeve and call the whole thing compliant. Fourth: missing or incomplete documentation. NFPA 101 and IBC require the installer to document each penetration with the UL system number, device used, cable types, and quantities. Fire marshals increasingly require photo documentation. Fifth: improper annular space. Most systems require a specific gap between the cable bundle and the sleeve opening, filled with the listed sealant to a minimum depth. Skip the sealant or apply it too thin and the system fails.

One hospital project we worked had 340 penetrations rejected because the previous contractor used the right sleeves with the wrong sealant. That's $85,000 in rework that proper documentation would have prevented.

Fire Marshal Inspection Requirements and Documentation

Fire marshals have gotten significantly more thorough about firestop inspections in the last five years. Here's what they look for and what you need to have ready. Each penetration needs a label or tag showing the UL system number. Many jurisdictions now require a firestop log listing every rated penetration in the building with its location, barrier type, system number, installer name, and date. Some AHJs (Authorities Having Jurisdiction) require third-party special inspection for firestop installations, particularly in healthcare occupancy (Group I) and high-rise buildings.

The International Firestop Council (IFC) offers the FM-1 and FM-2 certifications for firestop mechanics and inspectors. While not universally required by code, many general contractors and building owners mandate IFC-certified installers. From a practical standpoint, take photos of every penetration before and after firestopping. Include a ruler or scale reference in the photo showing sealant depth. Keep copies of all UL system detail sheets on site.

When the fire marshal walks the job, the difference between a 15-minute inspection and a two-week delay is having that documentation binder ready. Digital firestop management systems like Hilti® CFS-DM are becoming standard on large commercial projects for exactly this reason.

Common Questions

Frequently Asked Questions

For 18 Cat6a cables (roughly 0.30" OD each), a single 4" Hilti Speed Sleeve won't cut it. The UL listing for CP 653 in a 4" core drill typically maxes out around 15-19 Cat6a cables depending on the specific system number. You have two good options: use two 2" Speed Sleeves and split the bundle 9/9, or go with a single STI EZ Path EZD44+ which handles higher cable counts in its rectangular opening. Run your actual cable mix through this calculator to confirm the exact capacity before ordering. The cost difference between devices is less painful than failing a fire marshal inspection.

Five things account for about 90% of firestop rejections. Missing UL system number labels on the penetration is number one. Second is using the wrong firestop sealant. Even if you installed a Hilti sleeve, using a non-Hilti sealant may void the listing because the UL system was tested with a specific sealant product and depth. Third: overfilling the sleeve beyond the tested cable count. Fourth: insufficient sealant depth, which most systems specify as a minimum of 5/8" to 1". Fifth: no documentation. Many AHJs now require a firestop log listing every penetration with its system number, location, and installer. Having that binder ready turns a potential shutdown into a 15-minute walkthrough.

From a firestop perspective, yes. The UL system listings typically test with cable bundles by outside diameter, not by cable function. A 0.25" OD Cat6 cable and a 0.25" OD 14/2 fire alarm cable occupy the same space in the sleeve. However, check NEC Article 300.3 and 760.136 for separation requirements. Power-limited fire alarm circuits (Class 2/3) can share a raceway with communications cables but not with line-voltage wiring. Also verify the specific UL system detail sheet covers both cable types. Some systems are tested only with specific cable categories.

It depends on the device size comparison. A 4" Hilti CP 653 Speed Sleeve has a round opening with roughly 12.6 sq inches of cross-section. An STI EZ Path EZD33 (3-gang) has a rectangular opening that provides roughly 13.5 sq inches. The EZD44+ (4-gang) jumps to about 21 sq inches. So gang-for-gang at the larger sizes, EZ Path holds more cable. But the real difference is re-enterability. Speed Sleeves use intumescent material that's harder to work with after the initial install. EZ Path devices have removable pads that let you add or remove cables without destroying the fire seal. For buildings where cable changes happen regularly, that labor savings matters more than raw capacity.

Code doesn't universally require certification, but the trend is heading that way. IBC Section 714.3.2 requires a "special inspection" for penetration firestop systems in certain occupancies, which means the installer's work must be verified by a qualified inspector. Many general contractors and building owners now mandate International Firestop Council (IFC) FM-1 certification for the installers. Healthcare facilities (Group I occupancy) almost always require certified firestop mechanics.

Even where certification isn't mandated, having IFC-certified installers on your crew reduces rejection rates dramatically. The certification costs about $300 and covers the practical installation skills that prevent the common mistakes we see on job sites.

Build a penetration log spreadsheet with these columns: penetration ID number, floor and grid location, barrier type and rating (e.g., "2-hour fire wall"), UL system number, device installed, cable types and quantities, sealant product and depth, installer name, date, and photo reference. Take two photos of each penetration: one showing the cables before sealing, one showing the completed firestop with a ruler indicating sealant depth. Print the relevant UL system detail sheet and keep it in the log binder.

Some jurisdictions accept digital logs through platforms like Hilti CFS-DM, but always have a printed backup on site. This documentation package turns a potentially adversarial inspection into a straightforward verification.

This is where your initial device selection really matters. With STI EZ Path devices, you remove the intumescent pad, pull new cables, and replace the pad. The system is designed for this and the re-entry doesn't void the UL listing as long as you stay within the tested cable capacity. With Hilti Speed Sleeves, adding cables means removing the existing intumescent material, pulling cables, and re-firestopping the entire penetration with new material. That's a full rework.

For Hilti Modular Sleeves, you can sometimes add cables to empty channels without disturbing existing ones, depending on the specific system. Bottom line: if the building will see cable additions over its lifetime (most do), factor re-enterability into your device choice upfront. The cost difference at installation is small compared to the labor cost of rework.

Both wall and floor penetrations require firestopping, but the UL system numbers are different for each orientation. A system tested and listed for wall penetrations (W-L prefix in UL numbering) cannot be used in floors without a separate floor listing (F-L prefix). Gravity affects how intumescent material performs during a fire. Always verify the UL system detail sheet specifies "through-penetration firestop system" for your specific orientation.

Hilti Speed Sleeves, Modular Sleeves, and STI EZ Path devices all have both wall and floor listings, but the maximum cable counts may differ between orientations. This calculator shows capacities based on the device, so check the UL detail sheet for orientation-specific limits on your project.

Hilti® and Speed Sleeve® are registered trademarks of Hilti Corporation. STI® and EZ Path® are registered trademarks of Specified Technologies, Inc. This tool is provided by TSS USA and is not affiliated with, endorsed by, or sponsored by Hilti or Specified Technologies. Product data is sourced from publicly available manufacturer specifications.

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TSS USA. (2025). Fire Sleeve Fill Calculator. Retrieved from https://tssusa.net/fire-sleeve-fill-calculator/

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Last Updated: June 1, 2025

Cable capacities are based on manufacturer UL-tested data from Hilti and Specified Technologies (STI) published specifications. Fill limits reflect tested system capacities using interpolated lookup tables, not NEC percentage-based fill calculations. Always verify against the specific UL system detail sheet for your installation.

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