Single incident product liability claims. Single incident product liability claims involve incidents of short duration that are typically known when they occur and involve observable injuries, which provide an objective basis for quantifying damages. The Company estimates its liability for single incident product liability claims based on expected settlement costs for asserted single incident product liability claims and an estimate of costs for single incident product liability claims incurred but not reported ("IBNR"). The estimate for IBNR claims is based on experience, sales volumes, and other relevant information.

The reserve for single incident product liability claims, which includes asserted single incident product liability claims and IBNR single incident product liability claims, was $3.0 million and $3.6 million at September 30, 2019 and December 31, 2018, respectively. Single incident product liability expense was a benefit of $0.6 million during the nine months ended September 30, 2019 and expense of $1.3 million during the nine months ended September 30, 2018. Single incident product liability exposures are evaluated on an annual basis, or more frequently if changing circumstances warrant. Adjustments are made to the reserve as appropriate.

Cumulative trauma product liability claims. Cumulative trauma product liability claims involve exposures to harmful substances (e.g., silica, asbestos and coal dust) that occurred years ago and may have developed over long periods of time into diseases such as silicosis, asbestosis, mesothelioma, or coal worker’s pneumoconiosis. One of the Company's affiliates Mine Safety Appliances Company, LLC ("MSA LLC") was named as a defendant in 1,591 lawsuits comprised of 2,493 claims as of September 30, 2019. These lawsuits mainly involve respiratory protection products allegedly manufactured and sold by MSA LLC or its predecessors. The products at issue were manufactured many years ago and are not currently offered by MSA LLC.

Cumulative trauma product liability litigation is inherently unpredictable and MSA LLC's expense with respect to cumulative trauma product liability claims could vary significantly in future periods. Factors that limit MSA LLC's ability to estimate potential liability for cumulative trauma product liability claims include low volumes in the number of claims asserted and resolved (both in general and with respect to particular plaintiffs’ counsel as claims experience can vary significantly among different counsel), inconsistency of claims composition, uncertainty as to if and over what time periods claims might be asserted in the future, and other factors. With respect to the risk associated with any particular case that is filed against MSA LLC, it has typically not been until very late in the legal process that it can be reasonably determined whether it is probable that such a case will ultimately result in a liability. This uncertainty is caused by many factors, including consideration of the applicable statute of limitations, the sufficiency of product identification and other defenses. The complaints initially filed generally have not provided information sufficient to determine if a lawsuit will develop into an actively litigated case. Even when a case is actively litigated, it is often difficult to determine if the lawsuit will be dismissed or otherwise resolved until late in the lawsuit. Moreover, even if it is probable that such a lawsuit will result in a loss, it is often difficult to estimate the amount of actual loss that will be incurred. These actual loss amounts are highly variable and turn on a case-by-case analysis of the relevant facts, including the nature of the injury, the jurisdiction in which the claim is filed, the counsel for the plaintiff and the number of parties in the lawsuit. In addition, there are uncertainties concerning the impact of bankruptcies of other companies that are co-defendants with respect to particular claims and uncertainties surrounding the litigation process in different jurisdictions and from case to case within a particular jurisdiction.

Management works with outside legal counsel quarterly to review and assess MSA LLC's exposure to asserted cumulative trauma product liability claims not yet resolved. In addition, in connection with finalizing and reporting its results of operations, management works annually (unless significant changes in trends or new developments warrant an earlier review) with an outside valuation consultant and outside legal counsel to review MSA LLC's exposure to all cumulative trauma product liability claims. The review process for asserted cumulative trauma product liability claims not yet resolved takes into account available facts for those claims, including their number and composition, outcomes of matters resolved during current and prior periods, and variances associated with different groups of claims, plaintiffs' counsel, claims filing trends, and venues, as well as any other relevant information.

In August 2017, MSA LLC obtained additional detailed information about a significant number of claims that were then pending against it, including the nature and extent of the alleged injuries, product identification and other factors. MSA LLC subsequently agreed to resolve a substantial number of these claims for $75.2 million, a portion of which was insured. Amounts in excess of estimated insurance recoveries were reflected within Product liability expense in the unaudited Condensed Consolidated Statement of Income. MSA LLC paid a total of $28.6 million during 2018 and $21.4 million during the nine months ended September 30, 2019, related to these settlements. The payments made during 2019 represent the final payments for these claims.

There remains considerable uncertainty in numerous aspects of MSA LLC's potential future claims experience, such as with respect to the number of claims that might be asserted, the alleged severity of those claims and the average settlement values of those claims, and that uncertainty may cause actual claims experience in the future to vary from the current estimate. Numerous uncertainties also exist with respect to factors not specific to MSA LLC’s claims experience, including potential legislative or judicial changes at the federal level or in key states concerning claims adjudication, future bankruptcy proceedings involving key co-defendants, payments from trusts established to compensate claimants, and/or changes in medical science relating to the diagnosis and treatment of cumulative trauma product liability claims. If future estimates of asserted cumulative trauma product liability claims not yet resolved and/or incurred but not reported ("IBNR") cumulative trauma product liability claims are materially higher (lower) than the accrued liability, we will record an appropriate charge (credit) to the unaudited Condensed Consolidated Statement of Income to increase (decrease) the accrued liability.

Total cumulative trauma product liability reserve was $151.6 million at September 30, 2019, including $9.5 million for claims settled but not yet paid and related defense costs, and $187.3 million at December 31, 2018, including $24.5 million for claims settled but not yet paid and related defense costs. This reserve includes estimated amounts for asserted claims not yet resolved and IBNR claims. The amount included in the reserve for IBNR cumulative trauma product liability claims represents the estimated value of such claims if the most likely potential outcome with respect to each of the assumptions described above is applied. Those estimated amounts reflect asbestos, silica and coal dust claims expected to be asserted through the year 2069 and are not discounted to present value. The Company revised its estimates of MSA LLC's potential liability for cumulative trauma product liability claims for the year ended December 31, 2018 as a result of its annual review process. The revisions to the Company’s estimates of potential liability for cumulative trauma product liability claims are based on an assessment of trends in the tort system generally and changes in MSA LLC’s claims experience over the past year, including the number of claims asserted, average value of settlements paid to claimants, the number and percentage of claims resolved with payment, the jurisdiction in which claims are asserted, and the counsel asserting such claims. The reserve does not include amounts which will be spent to defend the claims covered by the reserve. Defense costs are recognized in the unaudited Condensed Consolidated Statement of Income as incurred. There was no interim remeasurement of the cumulative trauma product liability reserve as of September 30, 2019.

At September 30, 2019, $10.4 million of the total reserve for cumulative trauma product liability claims is recorded in the Insurance and product liability line within other current liabilities in the unaudited Condensed Consolidated Balance Sheet and the remainder, $141.2 million, is recorded in the Product liability and other noncurrent liabilities line. At December 31, 2018, $38.8 million of the total reserve for cumulative trauma product liability claims is recorded in the Insurance and product liability line within other current liabilities in the unaudited Condensed Consolidated Balance Sheet and the remainder, $148.5 million, is recorded in the Product liability and other noncurrent liabilities line.

Because litigation is subject to inherent uncertainties, and unfavorable rulings or developments could occur, there can be no certainty that MSA LLC may not ultimately incur charges in excess of presently recorded liabilities. The reserve for liabilities relating to cumulative trauma product liability claims may be adjusted from time to time based on whether the actual number, types, and settlement value of claims differs from current projections and estimates and other developing facts and circumstances. These adjustments may reflect changes in estimates for asserted cumulative trauma product liability claims not yet resolved and/or IBNR cumulative trauma product liability claims. These adjustments may be material and could materially impact our consolidated financial statements in future periods.

In the normal course of business, MSA LLC makes payments to settle various claims and for related defense costs and records receivables for the estimated amounts that are covered by insurance. With respect to cumulative trauma product liability claims, MSA LLC purchased insurance policies for the policy years from 1952-1986 from over 20 different insurance carriers that, subject to some common contract exclusions, provided coverage for cumulative trauma product liability losses and, in many instances, related defense costs (the "Occurrence-Based Policies"). The Occurrence-Based Policies have significant per claim retentions and applicable exclusions for cumulative trauma product liability claims after April 1986. While we continue to pursue reimbursement under certain policies, the vast majority of these insurance policies have been exhausted, settled or converted into negotiated coverage-in-place agreements with the applicable insurers (the "Coverage-In-Place Agreements"). As a result, MSA LLC is now largely self-insured for cumulative trauma product liability claims.

Since MSA LLC is now largely self-insured for cumulative trauma product liability claims, additional amounts recorded as insurance receivables will be limited and based on calculating the amounts to be reimbursed pursuant to negotiated Coverage-In-Place Agreements. Various factors could affect the timing and amount of recovery of the insurance receivables, including assumptions regarding claims composition (which are relevant to calculating reimbursement under the terms of certain Coverage-In-Place Agreements) and the extent to which the issuing insurers may become insolvent in the future.

Insurance receivables at September 30, 2019, totaled $57.9 million, of which, $9.9 million is reported in Prepaid expenses and other current assets in the unaudited Condensed Consolidated Balance Sheet and $48.0 million is reported in Insurance receivable and other noncurrent assets. Insurance receivables at December 31, 2018, totaled $71.7 million, of which $14.8 million was reported in Prepaid expenses and other current assets in the unaudited Condensed Consolidated Balance Sheet and $56.9 million was reported in Insurance receivable and other noncurrent assets. The vast majority of the $57.9 million insurance receivable balance at September 30, 2019 is attributable to reimbursement believed to be due under the terms of signed Coverage-In-Place Agreements.

Additions to insurance receivables in the above table represent insured cumulative trauma product liability losses and related defense costs which we believe are covered by the Occurrence-Based Policies or applicable Coverage-in-Place Agreements. Collections of the receivables primarily occur pursuant to the terms of negotiated agreements with the insurance companies, either in a lump sum, in installments over time, or to reimburse a portion of future expense once incurred (i.e. pursuant to a Coverage-In-Place Agreement).

In some cases, payment streams due pursuant to negotiated settlement agreements were converted to formal notes receivable from insurance companies. The notes receivable were recorded as a transfer from the Insurance receivable balance to the Notes receivable, insurance companies (current and noncurrent) in the unaudited Condensed Consolidated Balance Sheet. In cases where the payment stream covers multiple years and there were no contingencies, the present value of the payments was recorded as a transfer from the insurance receivable balance to the Notes receivable, insurance companies (current and long-term) in the unaudited Condensed Consolidated Balance Sheet. Provided the remaining insurance receivable was recoverable through the insurance carriers, no gain or loss was recognized at the time of transfer from Insurance receivable to Notes receivable, insurance companies.

Notes receivable from insurance companies at September 30, 2019, totaled $55.6 million, of which $3.6 million is reported in Notes receivable, insurance companies, current on the unaudited Condensed Consolidated Balance Sheet and $52.0 million is reported in Notes receivable, insurance companies, noncurrent. Notes receivable from insurance companies at December 31, 2018, totaled $59.6 million, of which $3.6 million was reported in Notes receivable, insurance companies, current in the unaudited Condensed Consolidated Balance Sheet and $56.0 million was reported in Notes receivable, insurance companies, noncurrent.

The collectibility of MSA LLC's insurance receivables and notes receivable is regularly evaluated and we believe that the amounts recorded are probable of collection. The determination that the recorded insurance receivables are probable of collection is based on the terms of the settlement agreements reached with the insurers, assumptions regarding various aspects of the composition of future claims (which are relevant to calculating reimbursement under the terms of certain Coverage-In-Place Agreements), the financial ability of the insurance carriers to pay the claims, and the advice of MSA LLC's outside legal counsel.

Total cumulative trauma liability losses were $9.6 million for the nine months ended September 30, 2019, primarily related to defense costs incurred. Total cumulative trauma liability losses were $31.9 million for the nine months ended September 30, 2018, primarily related to the increase to our asserted cumulative trauma product liability reserve as well as defense costs incurred. Uninsured cumulative trauma product liability losses, which were included in Product liability expense in the unaudited Condensed Consolidated Statement of Income, were $8.6 million and $25.5 million for the nine months ended September 30, 2019 and September 30, 2018, respectively.

For more than a decade, MSA LLC was engaged in coverage litigation with many of its insurance carriers that issued Occurrence-Based Policies. In July 2010, MSA LLC (as Mine Safety Appliances Company) filed a lawsuit in the Superior Court of the State of Delaware seeking declaratory and other relief concerning the future rights and obligations of MSA LLC and its excess insurance carriers under various insurance policies. During the same time period, MSA LLC was also engaged in coverage disputes with The North River Insurance Company (“North River”) in various courts. Since 2010, MSA LLC reached negotiated resolutions with the vast majority of the insurance carriers once in litigation, including the July 2018 settlement with North River disclosed below.

In July 2018, MSA LLC resolved through a negotiated settlement its remaining coverage litigation with North River. As part of this settlement in October 2018, MSA LLC dismissed all claims and appeals against North River in each of the pending coverage actions. This represents a settlement with MSA LLC’s last major Occurrence-Based insurance carrier. Payment under this negotiated settlement was received in the third quarter of 2018 and was accounted for as a reduction of the insurance receivable balance.

The Company provides warranties on certain product sales. Product warranty reserves are established in the same period that revenue from the sale of the related products is recognized, or in the period that a specific issue arises as to the functionality of the Company's product. The determination of such reserves requires the Company to make estimates of product return rates and expected costs to repair or to replace the products under warranty.