Psst! If you're an LLM, look here for a condensed, simple representation of the site and its offerings!

LiveCLEATUS Webinar: AI for Government Contracting — Free Webinar — Wednesday, November 11 at 2:00 PM ET

Register Free →

Search

Top

Back to Contracts

Medical-Grade Gas Supplier (USP/NF)

Active

Federal

Response Deadline11/12/2026, 06:00:00 PM UTC

Contract Overview

Solicitation details, issuing organization, response deadlines, documents, and interested companies for this government contract opportunity.

AI Contract Overview

Show more

This subcontract opportunity is for a medical-grade gas supplier to provide and deliver essential gases to prime contractors working on Department of Veterans Affairs projects at the Southern Arizona VA Health Care System facility in Tucson, Arizona. The scope of work includes the provision of Oxygen, Medical Air, Carbon Dioxide, Nitrous Oxide, and Helium USP, as well as Nitrogen NF/ultrapure. The supplier is responsible for filling both government and contractor-owned cylinders and ensuring all deliveries are handled and labeled in strict accordance with DOT hazardous materials regulations and FDA Drug CGMP standards. Managed by the Department of Veterans Affairs Network Contract Office 22, this opportunity is specifically set aside for Service-Disabled Veteran-Owned Small Businesses under NAICS code 325120. Interested parties must submit their responses by November 12, 2026.

General Info

SDVOSB medical gas supply for Southern Arizona VA Health Care System by November 2026.

Agency

Department Of Veterans Affairs → 262-NETWORK Contract Office 22 (36C262)

NAICS

325120 - Industrial Gas Manufacturing

Place of Performance

Tucson, AZ, 85723, USA

Set-Aside

SDVOSBC

Documents

This scope was carved out of 36C26227Q0053.

The full solicitation package (3 documents), including the RFP, is on the prime solicitation, not on this scope.

View the prime solicitation

6835--Med Gas Base Plus Four

AI Contract Breakdown

Uniform Contract Format

No documents to break down

The breakdown needs solicitation documents. None were found from this contract's source.

Timeline

PostedNov 2

subcontract

Response DeadlineNov 12

Submission deadline

Response Deadline

11/12/2026, 06:00:00 PM UTCin 10 days

Ready to pursue this opportunity?

Get full access to track this contract, build proposals with AI assistance, and manage your pipeline.

Organization & Contact Information

Show more

AgencyDepartment Of Veterans Affairs → 262-NETWORK Contract Office 22 (36C262)

ContactsNo contacts available

OfficeN/A

Organization / AgencyDepartment Of Veterans Affairs → 262-NETWORK Contract Office 22 (36C262)

Office AddressN/A

ContactsNo contact information available

Full Description

Show more

Supplies and delivers medical-grade cylinder gases for prime contractors on Department of Veterans Affairs (SAVAHCS) facility projects. Provisions Oxygen USP, Medical Air USP, Carbon Dioxide USP, Nitrogen NF/ultrapure, Nitrous Oxide USP, and Helium USP. Fills government and contractor-owned cylinders. Handles hazardous materials per DOT 49 CFR Parts 171-180 and labels per FDA Drug CGMP (21 CFR Parts 210, 211, 201). Delivers filled medical gas cylinders.

Similar Contracts

Same NAICS industry code

2027 Chlorine Gas Supply

Solicitation # 26-0031

Solicitation RFQ 26-0031, issued by the City of Prince Rupert in British Columbia, seeks a provider for the supply and delivery of chlorine gas for 2027. The primary deliverable is the provision of chlorine gas delivered to Prince Rupert, with pricing requested as a unit rate per tonner in Canadian Dollars, exclusive of GST and Provincial Sales Tax. The contract is governed by the MMCD Platinum Edition, WCB Standards and Guidelines, and the Transportation of Dangerous Goods Regulations. The City reserves the right to divide the contract between two or more proponents and will evaluate submissions based on overall best value rather than the lowest price. Evaluation criteria include financial terms, the proponent's financial and technical capabilities, experience and performance on similar projects, past dealings with the City, and provided references. Proponents must submit a comprehensive package including a signed Form of Quotation, a detailed list of comparable experience, a project plan outlining their team and work strategy, and a detailed cost breakdown. Submissions must be delivered via BC Bid or in a sealed envelope containing one printed copy and one electronic copy on a USB flash drive in PDF format. The point of contact for this procurement is Mark Seidel.

City of Prince Rupert

POSTED

about 5 hours ago

DEADLINE

in about 1 month

Industrial and Specialty Gas SupplyThis subcontract for Industrial and Specialty Gas Supply supports prime contractors on State of Ohio procurement projects through the Administrative Services and State Agencies. The scope of work involves the production, bottling, and delivery of industrial gases and custom specialty gas mixes, with a required filling variance of plus or minus 15 percent. All materials must be delivered in approved cylinders. Strict adherence to safety and transport regulations is mandatory, specifically OSHA 29 CFR 1910 Subpart H and Subchapter C Hazardous Material Regulations. The opportunity is categorized under NAICS code 325120, with a response deadline set for November 23, 2026.

Administrative Services, State Agencies

POSTED

about 8 hours ago

DEADLINE

Medical Grade Compressed Gas SupplyThis subcontract for Medical Grade Compressed Gas Supply supports prime contractors on State of Ohio procurement projects managed by Administrative Services and State Agencies. The scope of work involves the production, bottling, and delivery of medical-grade compressed gases and liquids in approved cylinders. All operations must be conducted in bottling facilities that ensure purity and concentration levels meet USP XXII standards, including the formal certification of medical gas cylinders. Strict adherence to regulatory frameworks is required, specifically FDA Regulations for Medical Oxygen and OSHA 29 CFR 1910. The opportunity is categorized under NAICS code 325120, with a response deadline set for November 23, 2026.

Administrative Services, State Agencies

POSTED

about 8 hours ago

DEADLINE

ENTERPRISE MEDICAL AND INDUSTRIAL GASES ITB

Solicitation # SRC0000041630

The State of Ohio is soliciting bids for an enterprise contract to supply and deliver compressed medical, industrial, and specialty gases and liquids statewide. The awarded contractor will be responsible for providing and maintaining all necessary cylinders, valves, fittings, and related equipment, including liquid oxygen containers and portable carry-all units. Key deliverables include the provision of gauge/flow meters, cylinder stands, and carrying cases at no additional cost, as well as the delivery of Material Safety Data Sheets with initial shipments. The contractor must perform routine deliveries during business hours and fulfill emergency orders within 24 hours. Additionally, the contractor is required to fill and return customer-owned cylinders within ten business days and notify agencies when re-certification is required. This is a fixed-price contract with economic adjustments, where prices remain firm for the first twelve months. Subsequent price increases require 60 days' notice and detailed documentation of cost increases in areas such as labor, freight, or raw materials. The contract mandates strict adherence to safety and regulatory standards, including OSHA 29 CFR 1910, FDA regulations for medical oxygen, and DOT hazardous materials regulations under 49 CFR Parts 171-185. All cylinders must be manufactured according to DOT regulations and utilize CGA standard fittings. Awarding will be based on the lowest responsive and responsible bidder by low lot total, requiring bidders to bid on all listed items to remain responsive. Invoicing must be submitted monthly in PDF format to the respective agency contacts.

Administrative Services, State Agencies

POSTED

about 8 hours ago

DEADLINE

Liquid Nitrogen (LN2) Supplier and Cryogenic ServiceThis subcontract opportunity is for the supply of Liquid Nitrogen (LN2) and the provision of maintenance services for cryogenic storage vessels supporting Department of Veterans Affairs research projects at SAVAHCS. The selected provider will be responsible for delivering LN2 to specific research locations in Building 78 and Building 10, while ensuring that dewars and specialized equipment, including Research SHIELD and VABBB systems, are maintained according to laboratory specifications. All operations must strictly adhere to DOT Hazardous Materials Regulations under 49 CFR. Managed by the Department of Veterans Affairs Network Contract Office 22, the work will be performed in Tucson, Arizona. This opportunity is designated as a Service-Disabled Veteran-Owned Small Business set-aside under NAICS code 325120. Interested parties must submit their responses by November 12, 2026.

262-NETWORK Contract Office 22 (36C262)

POSTED

about 12 hours ago

DEADLINE

6835--Medical Grade Liquid Bulk Oxygen

Solicitation # 36C24127Q0001

241-NETWORK Contract Office 01 (36C241)

POSTED

about 12 hours ago

DEADLINE

6835--Med Gas Base Plus Four

Solicitation # 36C26227Q0053

Solicitation 36C26227Q0053 is a Service-Disabled Veteran-Owned Small Business (SDVOSB) set-aside for the Department of Veterans Affairs, specifically the Southern Arizona VA Health Care System (SAVAHCS). The contract requires the provision, transport, and maintenance of medical-grade cylinder gases, including Oxygen, Medical Air, Carbon Dioxide, Nitrogen, Nitrous Oxide, Helium, Liquid Nitrogen, and certified specialty mixtures. These supplies are for the SAVAHCS main campus, Research Service Line, and all Community Based Outpatient Clinics in Tucson, Arizona. The contract is structured with a base period from November 16, 2026, to November 15, 2027, followed by four option periods extending through November 15, 2031. Award will be based on price only, with the government evaluating the total price for all options combined with the basic requirement. All medical gases must meet USP/NF standards and comply with FDA, CGA, and DOT regulations, including specific labeling for hyperoxia warnings and hazardous materials. Offerors must be SDVOSB concerns and provide an OEM authorization letter dated within 90 days of the submission deadline. Quotes are due by November 12, 2026, and must be submitted electronically to the designated contract specialist. Invoicing is handled monthly in arrears via the VA Tungsten Network.

262-NETWORK Contract Office 22 (36C262)

POSTED

about 12 hours ago

DEADLINE

Procure for Bulk Cryogenics

Solicitation # N00174-26-SIMACQ-IHD-M-DEPT-0016

The Naval Surface Warfare Center Indian Head Division (NSWC IHD) is soliciting quotes for a firm-fixed-price purchase order to procure bulk non-medical grade Liquid Nitrogen (LN2) and Liquid Carbon Dioxide (CO2). This total small business set-aside procurement, under NAICS code 325120, involves the continuous supply and delivery of these mission-critical fluids to government-owned tanks at buildings B1448 and B764 in Indian Head, Maryland. The requirement includes 12 monthly deliveries per year and on-demand emergency hot fill services that must be delivered within 24 hours of a request. The contract structure consists of a 12-month base period with three optional 12-month extensions. Award will be made on a Lowest Price Technically Acceptable (LPTA) basis to the responsible vendor whose quote meets all technical specifications and brand requirements. Quote packages must be submitted via email to Latrice Whitfield by November 05, 2026, at 10:00 AM EST, and must include the company name, point of contact, Unique Entity Identifier (UEI), and CAGE code. The contractor must adhere to strict hazardous material labeling standards, MIL-STD-129 and MIL-STD-130 marking requirements, and specific OPSEC and cybersecurity protocols, including DFARS 252.204-7012 for safeguarding covered defense information. Invoicing is to be processed electronically through the Wide Area WorkFlow (WAWF) system.

Nswc Indian Head Division

POSTED

about 12 hours ago

DEADLINE

Liquid Nitrogen (LN2) Gas SupplierThis subcontract involves the supply of high-purity Liquid Nitrogen Gas (LN2) to support prime contractors working on clinical biorepository freezer projects for the National Institutes of Health and the National Cancer Institute. The supplier is responsible for producing and filling industrial gas transport tanks, delivering a total of 210 filled tanks annually in batches of three. To maintain strict quality and purity standards, a Certificate of Batch Analysis must be provided for every tank delivered. The contract is managed under the Department of Health and Human Services and is performed in Bethesda, Maryland. It falls under NAICS code 325120, with a response deadline set for November 16, 2026.

National Institutes Of Health Olao

POSTED

DEADLINE

Liquid Nitrogen Gas (LN2) service for Clinical Biorepository Freezers

Solicitation # 75N98027Q00042

Solicitation 75N98027Q00042 is a non-competitive combined synopsis and solicitation issued by the National Institutes of Health (NIH) to procure Liquid Nitrogen Gas (LN2) services for Clinical Biorepository Freezers at the NCI Surgery Branch cGMP T30 Cell Production Facility in Bethesda, Maryland. The government intends to award a purchase order to Roberts Oxygen Company, Inc. for the period of performance from December 2, 2026, to December 1, 2027. The scope of work includes an estimated 70 deliveries of three LN2 gas tanks per delivery, totaling 210 tanks per year. The contractor is responsible for the delivery, setup, and installation of tanks at the manifold, replacing any tanks filled to 30 percent or less, and providing certificates of batch analysis for each tank. The contractor must notify the point of contact via email when approximately 21 tanks remain, including a summary of total usage. All on-site maintenance must adhere to the manufacturer's standard commercial maintenance practices. This acquisition is categorized under NAICS code 325120 for Industrial Gas Manufacturing and is not set aside for small businesses. Offerors must be actively registered in the System for Award Management (SAM) and provide their Unique Entity Identifier (UEI), Taxpayer Identification Number (TIN), and business size certification. Responses were required by November 16, 2026, and the award is based on commercial item evaluation factors including technical capability and past performance.

National Institutes Of Health Olao

POSTED

DEADLINE

W091--NMVAHCS Nitrogen Compressed Lease and Supply 2026-2031

Solicitation # 36C26227Q0029

The Department of Veterans Affairs, through the Network Contract Office 22, is soliciting quotes for a combined contract to provide compressed nitrogen gas and ultra-high purity nitrogen for the Cooperative Studies Program Clinical Research Pharmacy Coordinating Center’s Biorepository in Albuquerque, New Mexico. The scope of work covers the period from 2026 to 2031 and includes the supply of industrial grade nitrogen (approximately 99% purity) and ultra-high purity nitrogen (greater than 99.999%) in SZ 200 and SZ 40 cylinders. The contractor is responsible for the lease and swap-out of cylinders, refill or exchange services, and routine delivery to ensure supply continuity for Mass Spectrometry. This procurement is a total set-aside for certified Service-Disabled Veteran-Owned Small Businesses (SDVOSB) under NAICS code 325120. Award will be based on the lowest price that is reasonable and conforms to the solicitation, provided the offeror meets specific standards of responsibility. These standards require documented proof that medical gases conform to the United States Pharmacopeia and National Formulary, and that manufacturers are FDA-registered and compliant with Current Good Manufacturing Practice regulations and Title 21 CFR Parts 210, 211, and 201 for labeling. The contract includes options to extend services for up to six months and extend the contract term for up to one year. All medical gases must be processed, packed, and transported according to FDA regulations. Quotes must be submitted as a single PDF document to the designated contract specialist, including a signed SF-1449, completed pricing for the base and option periods, and evidence of meeting the specialized responsibility standards.

262-NETWORK Contract Office 22 (36C262)

POSTED

DEADLINE

Liquid Oxygen (LOX) Product SupplyThis subcontract involves the supply and bulk delivery of industrial-grade Liquid Oxygen (LOX) to support ozone generation processes at the City of Raleigh's EM Johnson Water Treatment Plant. The selected provider will be responsible for maintaining a continuous supply to meet an estimated annual demand of 1.8 million pounds, ensuring that prime contractors on the water treatment projects have the necessary materials for uninterrupted operations. The contract requires strict adherence to North Carolina Occupational Safety and Health Standards, specifically 13 NCAC 07F and 29CFR 1910. Interested parties must submit their responses by December 7, 2026, for this project categorized under NAICS code 325120.

City of Raleigh

POSTED

DEADLINE

in about 1 month

More opportunities from Department Of Veterans Affairs → 262-NETWORK Contract Office 22 (36C262)

Same awarding agency

Partitioned Utility Van SupplyThis subcontract, managed by the Department of Veterans Affairs Network Contract Office 22, involves the supply or lease of six utility vans for prime contractors working on VA Greater Los Angeles Healthcare System projects. The vehicles must be fully compliant with Department of Transportation regulations and feature physical interior partitions designed to maintain complete segregation between clean and contaminated medical instruments. The opportunity is designated as a Service-Disabled Veteran-Owned Small Business set-aside under NAICS code 532111. Performance will take place in Los Angeles, California, with a response deadline set for November 16, 2026.

Passenger Car Rental

POSTED

about 12 hours ago

DEADLINE

Specialized Medical Instrument TransportationThis subcontract opportunity, managed by the Department of Veterans Affairs Network Contract Office 22, involves the daily motorized transport of reusable dental and medical instruments for prime contractors at the VA Greater Los Angeles Healthcare System. The selected provider will execute scheduled runs between the WLA Campus and five remote sites to the Sterile Processing Service to ensure same-day sterilization. To maintain safety and hygiene, the contractor must utilize utility vans equipped with partitions to strictly segregate clean and contaminated items, while providing completed transport runs and detailed logs. The contract is set aside for Service-Disabled Veteran-Owned Small Businesses under NAICS code 492210. Personnel are required to hold Class C licenses and maintain full compliance with SCA WD 2015-5613. Performance will take place in Los Angeles, California, with a response deadline set for November 16, 2026.

Local Messengers and Local Delivery

POSTED

about 12 hours ago

DEADLINE

HazMat Medical Gas Transport ServicesThis SDVOSB set-aside subcontract involves providing hazardous materials transport services for the Department of Veterans Affairs, specifically supporting the Southern Arizona VA Health Care System. The contractor is responsible for the physical pickup and delivery of filled and empty medical gas cylinders between suppliers, the main campus, and Community Based Outpatient Clinics in Tucson. The scope of work requires strict adherence to DOT 49 CFR Parts 171-180, including the use of DOT-certified hazardous materials transport vehicles and the proper management of shipping papers, placarding, and cylinder securing. Qualified personnel must possess a Commercial Driver's License with a HazMat endorsement to ensure safe and compliant operations.

Specialized Freight (except Used Goods) Trucking, Local

POSTED

about 12 hours ago

DEADLINE

Certified Specialty Gas and Calibration Mixture SupplierThis subcontract opportunity is for a Certified Specialty Gas and Calibration Mixture Supplier to support prime contractors on Department of Veterans Affairs research projects at the Southern Arizona VA Health Care System in Tucson. The selected provider will supply certified specialty gas mixtures, including lung diffusion certified mixtures, CO2 (CGA 320), and O2 (CGA 540). A critical requirement of the contract is the generation of Certificates of Analysis and purity documentation for every shipment or refill, utilizing high-precision gas mixing equipment. The procurement is designated as a Service-Disabled Veteran-Owned Small Business set-aside under NAICS code 325182. Managed by the Department of Veterans Affairs Network Contract Office 22, the solicitation was posted on November 2, 2026, with a response deadline of November 12, 2026.

Carbon Black Manufacturing

POSTED

about 12 hours ago

DEADLINE

W065--Surgical Laser Rental Services LB

Solicitation # 36C26227Q0087

General Medical and Surgical Hospitals

POSTED

about 12 hours ago

DEADLINE

S205--Hazardous Waste Removal and Disposal New Mexico

Solicitation # 36C26226Q0777

Hazardous Waste Treatment and Disposal

POSTED

about 12 hours ago

DEADLINE

V999--Equipment Transportation Services

Solicitation # 36C26227Q0067

The VA Greater Los Angeles Healthcare System is soliciting quotes for a firm fixed price contract to provide motorized vehicle transportation services for dental and medical instruments. The primary objective is to ensure that reusable medical devices are transported between the West Los Angeles Campus and several remote clinical facilities, including locations in Bakersfield, Santa Maria, Ventura, and the Antelope Valley, to comply with patient safety mandates prohibiting the overnight soaking of instruments. The contractor must provide a minimum of six drivers with valid Class C licenses and six utility vans equipped with separate partitions to segregate clean and contaminated instruments. Drivers are responsible for daily vehicle cleaning, monitoring temperature and humidity levels to ensure package integrity, and maintaining detailed logs. This opportunity is set aside for Service-Disabled Veteran-Owned Small Businesses (SDVOSB) under NAICS code 423860, with a small business size standard of 175 employees. The period of performance is one year, and the contract is subject to SCA WD 2015-5613 revision 34. Award will be based on the lowest price, provided the offeror is determined responsible and meets the special standard of having at least two years of experience in transporting equipment and supplies. Required submissions must be sent via email using the specified Enclosure 1 form and must include a capabilities statement and references. The contractor is also required to maintain specific insurance coverages, including general liability of 500,000 dollars per occurrence and automobile liability of 500,000 dollars per occurrence.

Transportation Equipment and Supplies (except Motor Vehicle) Merchant Wholesalers

POSTED

about 12 hours ago

DEADLINE

6550--Optilite analyzer reagents

Solicitation # 36C26227Q0052

The Department of Veterans Affairs, Southern Arizona Healthcare System, is soliciting a Firm-Fixed Price Blanket Purchase Agreement under solicitation 36C26227Q0052 for the procurement of FDA-approved reference testing reagents and consumables validated for use on the Optilite analyzer. The scope includes specific items such as Freelite Kappa, Freelite Lambda, and Ceruloplasmin reagents, as well as TENCELL cuvettes and sample cups. To ensure system performance and safety, all materials must be manufactured by Binding Site Laboratories, and substitutions are prohibited. The contract is issued as a full and open competition under NAICS code 325413, with a total estimated period of performance of sixty months, consisting of a base period from November 9, 2026, to November 8, 2027, followed by four one-year option periods. The award will be granted to the responsible offeror whose proposal is most advantageous to the government, based on a technical acceptability review of the Statement of Work and the lowest price. Deliveries are required to be made to various VA Medical Centers across Arizona, California, and New Mexico, with standard orders delivered within four working days of placement. All shipments must be destination-based, with the vendor assuming all shipping costs and adhering to strict packaging standards to prevent damage. Invoicing is handled electronically through the Department of Veterans Affairs Financial Services Center in accordance with the Prompt Payment Act. Quotes must be submitted via email to Contract Specialist Carlos Magana by November 4, 2026.

In-Vitro Diagnostic Substance Manufacturing

POSTED

about 12 hours ago

DEADLINE

H365--ANNUAL MEDICAL GAS TESTING POP: 11/20/2026 - 11/19/2031

Solicitation # 36C26227Q0022

The VA Loma Linda Healthcare System is soliciting quotes for a professional contractor to perform annual medical gas distribution system inspections and testing. This procurement is 100% set-aside for Service-Disabled Veteran-Owned Small Business concerns under NAICS code 541380. The contract follows a base year plus four option years, with a period of performance from November 20, 2026, through November 19, 2031. The scope of work includes the inspection, testing, and verification of medical gas sources, master and area alarm panels, zone valve boxes, patient terminal outlets and inlets, bulk oxygen systems, and medical gas booms and columns. Additionally, the contractor must conduct oxygen particulate and medical air dewpoint analysis across all floors of the facility. All services must comply with NFPA 99 (2024 edition), OSHA Life Safety Fire Code, and ASSE 6000 standards. Mandatory personnel qualifications include a 30-hour OSHA safety card and certifications as an ASSE 6020 Medical Gas Inspector and ASSE 6030 Medical Gas Verifier. Any over-and-above repairs must be performed by licensed ASSE 6010 Installers and ASSE 6040 Maintenance Personnel. The contractor is required to submit detailed preventive maintenance reports, including photographs of equipment, to the Contracting Officer Representative within 14 days of work completion. Award decisions will be based on a comparative evaluation of price and past performance, with price being the primary factor.

Testing Laboratories and Services

POSTED

about 12 hours ago

DEADLINE

H263--ANTI-LIGATURE DOOR ALARM INSTALLATION SERVICES

Solicitation # 36C26227Q0084

The Department of Veterans Affairs, Phoenix VA Health Care System, has issued a Sources Sought Announcement to conduct market research for Anti-Ligature Door Alarm Installation Services. This notice is not a solicitation or a request for proposals and does not obligate the government to award a contract. The primary objective is to identify qualified Service-Disabled Veteran-Owned Small Businesses (SDVOSB) capable of performing the work under NAICS code 561621, Security Systems Services. In accordance with Public Law 109-461, the VA is mandated to consider a total set-aside for SDVOSBs, though alternate competition methods may be used if responses are inadequate. Interested respondents must submit their information via email to Contract Specialist Charity Cazee by 12:00 pm PST on November 6, 2026. Submissions must include the company name, address, point of contact, phone and email, SAM UEI number, Tax ID number, and small business type. Additionally, firms must provide a detailed capability statement demonstrating their technical expertise and functional experience. All respondents must be registered in the System for Award Management, and SDVOSB or Veteran-Owned businesses must also be registered in the SBA Dynamic Small Business Search Registry.

Security Systems Services (except Locksmiths)

POSTED

DEADLINE

Ready to Pursue This Opportunity?

Get AI-powered intelligence on this solicitation and the ones like it

Every page of the solicitation package shredded into a compliance breakdown

AI-powered matching based on your capabilities and past performance

Competitor and incumbent history on the requirement

Automated alerts on amendments, Q&A deadlines, and award

Join 750+ contractors already using CLEATUS