Selection of a safety light curtain starts with three orthogonal axes: the IEC/EN 61496-1 Type (2 or 4), the detection resolution (14 / 30 / 60 mm and beyond), and the housing/sealing class (IP40 indoor vs IP67 washdown) [S1][S4][S5].
Across 2024-2026 OEM catalogues, these three axes line up with specific applications: finger-protection (14 mm) for points of operation, hand-protection (30 mm) for access guarding, and 60 mm / multibeam for perimeter and area presence detection on cells and robots [S2][S5][S6][S9].
IEC/EN 61496-1 Type 2 vs Type 4 — risk class and PL/SIL mapping
Banner's 2026 product page draws the line explicitly: "Type 4 safety light curtains protect personnel from injury and machines from damage by guarding points of operation, access, areas and perimeters," while "Type 2 safety light curtains are a cost-effective light curtain safety solution for guarding lower-risk applications, where the result of an accident is only a slight injury" [S2]. TE Connectivity's Compact line is offered in both "Type 2 - PL …" and Type 4 variants to the same standard, with the SLC range engineered to "ensure the protection of humans, machinery, and the environment" in industrial automation, robotics, and machinery [S4].
Pepperl+Fuchs' SLCT30 is a Type 2 device rated "SIL1 acc. to IEC 61508" with a -30 … 60 °C (-22 … 140 °F) operating envelope and protection heights to 2400 mm [S8]. The Type 4 SLC14, SLC30, and SLC60 siblings are described as "self-monitoring (type 4 according to IEC/EN 61496-1)" with optional ATEX certification for zone 2 and 22 dust atmospheres, illustrating how risk-tier and zone classification travel together [S5][S6][S9].
Resolution classes: 14 mm finger, 30 mm hand, 60 mm and multibeam area
Detection-object size sets the protected-field height and sensing range envelope, and the catalogue data shows three crisp tiers. Finger detection at 14 mm: the Pepperl+Fuchs SLC14-150-S delivers "Sensing range up to 5 m, Resolution 14 mm (finger protection), Protection field height up to 750 mm" in a Type 4, IP67 housing [S5]. Hand detection at 30 mm: the SLC30-1500-S pushes range to "up to 15 m" and height to 1650 mm, again Type 4 self-monitoring with OSSD outputs [S6]. Body/area at 60 mm: the SLC60-1200-S holds "Sensing range up to 15 m, Resolution 60 mm, Protective field height up to 1800 mm" with optional ATEX zone 2/22 [S9].
For wide-area presence detection, the Autonics BWPK series uses a multibeam through-beam configuration with a 10 mm PC/ABS housing, IP40 enclosure, and a 0.1-3 m operating range — explicitly a compact "picking sensor" rather than a per-safety-function guard [S1]. The contrast is the rule: as resolution coarsens, range and field height grow, and the device shifts from finger-guard to perimeter-guard duty.
Housing, sealing, and form factor: IP40 vs IP67 and slim housings
Sealing tracks the application environment, and the OEM spread is wide. Indoor pick-and-place and electronics assembly typically use IP40-class devices such as the Autonics BWPK, with its "flat and compact body (10 mm) made of high strength PC/ABS" and "mutual interference prevention function" plus "Light ON/Dark ON switching" via DIP switches [S1]. Food, beverage, pharmaceutical, and outdoor robotic cells demand IP67: the Pepperl+Fuchs SLC family ships at IP67 with "Potential-separated semiconductor design or with monitored, compelled connection NC-contacts" and integrated function/operating-reserve displays [S5][S6][S9].
Keyence attacks the space-constrained machine builder with two form factors. The SL-C series (EU catalogue page dated 2026-06-08) targets the general machine-safety market [S3], while the GL-S series offers a "slim type GL-SS" and a "flat type GL-SF" in an "ultra-thin housing … half the size of conventional curtains" with "built-in mounting" for fast install [S10]. Banner adds a third tier on top of the Compact Type 4 line: a "Heavy-Duty Type 4" range "for harsh industrial environments" alongside the standard Compact Type 4 [S2].
Safety outputs, integration, and the OSSD baseline
Output topology is where the Type 2 vs Type 4 difference is most concrete in the wiring cabinet. Type 4 Pepperl+Fuchs SLC devices provide "Safety outputs OSSD in potential-separated semiconductor design or with monitored, compelled connection NC-contacts" with Start/Restart disable and Master/Slave detection for cascaded fields [S5][S6][S9]. Type 2 SLCT30 carries the same self-test architecture but at SIL 1, a level the documentation states explicitly [S8].
Functional integration is increasingly bidirectional. AutomationDirect's "Safety Light Curtains (Category 4 / Type 4)" category page indexes the on-the-shelf options for US panel builders, including shipping-cut-off advisories around the July 2026 holiday window — useful as a real lead-time data point for North-American builds [S7]. TE Connectivity's "Compact Type 2 and Type 4 SLC" range is positioned around the same EN IEC 61496-1/-2 baseline, with both classes sharing a common footprint to simplify dual-risk-cell design [S4]. For broader machine-guard context, the safety barrier and safety fence encyclopaedia entries cover the physical perimeter hardware that typically flanks a light-curtain field.
Comparison: which Type, resolution, and IP fit which job
Using OEM data, three decision rules cover the bulk of 2026 specifications. Risk class: Type 4 / SIL 3 (PL e) is the default for points of operation, robot cells, and any hazard that can cause serious injury, while Type 2 / SIL 1 (PL c) is acceptable only where the worst credible injury is slight, per Banner's product-page definition [S2]. Resolution: 14 mm finger-guard is mandatory when the hazard is reached through the curtain at any operator hand position (SLC14-150-S: 5 m range, 750 mm height) [S5]; 30 mm hand-guard is the workhorse for access guarding at heights to 1650 mm and ranges to 15 m (SLC30-1500-S) [S6]; 60 mm or multibeam is for perimeter and area presence only, never for finger or hand reach-in (SLC60-1200-S: 15 m, 1800 mm; BWPK multibeam IP40) [S1][S9].
Environment: IP40 (Autonics BWPK) is acceptable only for dry, clean indoor aisles; IP67 with metal end-caps and OSSD outputs is the floor for washdown, outdoor, or ATEX zone 2/22 areas where the Pepperl+Fuchs SLC ATEX option is specified [S1][S5][S6]. Form factor: slim and flat (Keyence GL-SS/GL-SF, half the cross-section of legacy units) is chosen where the guard has to sit inside the machine frame, while Heavy-Duty Type 4 (Banner) is selected where impact and coolant are expected [S2][S10]. For comparison with adjacent PPE categories on a project bill of materials, see the safety glasses reference for the operator-side eye protection that complements these engineered guards.
Standards, sourcing, and what to verify on the datasheet
The harmonised baseline is EN IEC 61496-1/-2 for the electro-sensitive protective equipment itself, and IEC 61508 for the SIL claim; Pepperl+Fuchs cites both explicitly on Type 2 (SLCT30, SIL 1) and Type 4 (SLC14/30/60) variants, while TE Connectivity markets its Compact range "as per EN IEC 61496-1/-2" [S4][S5][S6][S8][S9]. Optional ATEX conformity to zone 2 (gas) and zone 22 (dust) is documented on the Pepperl+Fuchs SLC family for hazardous-area deployments, with the IP67 housing retained [S5][S6][S9].
On the datasheet, the four numbers to lock down before sign-off are: Type (2 or 4) per IEC/EN 61496-1, the SIL/PL claim per IEC 61508 and EN ISO 13849-1, resolution (14 / 30 / 60 mm or multibeam), and the IP rating against the washdown or dust exposure of the actual cell. For projects in adjacent plant rooms, steel strand types and classifications covers the structural tie-ins that support guard frames, and hearing protector advantages, disadvantages, and selection criteria addresses the operator-side PPE that complements engineered light curtains on a noisy cell.
Trackable signals for the next procurement cycle: confirm whether Banner's Heavy-Duty Type 4 line (2026-06-05 product page) extends its IP rating beyond Compact, watch for any 2026 Q3/Q4 Type 2 PL upgrade announcements against the SLCT30 baseline [S2][S8], and verify AutomationDirect's July 2026 shipping window before locking panel-build dates around the Independence Day closure [S7].