The first question for decision is whether or not the insurance carrier was on the risk during the .period of employee’s “¡last injurious exposure” to silicia dust so as to impose liability on the carrier.
Defendant employer insists that employee became disabled as disablement is defined by G.S. 97-54 on 5 July 1951. Dr. Swisher testified: “In my opinion Mr. Wright was incapacitated from performing any normal labor as ia stonecutter on July 5,1951.” Carrier was on the risk from 16 April 1951 to 16 July 1951. Defendant contends that the testimony of Dr. Swisher by fixing the date of disablement fixes the time of last injurious exposure, that the last day of injurious exposure was 5 July 1951, that the Commission should have found accordingly, that the Commission was in error in dismissing the carrier, and that the Superior Court was correct in reversing the Commission on this point.
Employee worked regularly from 16 July 1951 to 29 September 1951 for defendant and during this period was exposed to the hazards of silicosis. During this period he worked 52 full eight-hour days. Silicosis is a progressive and' often fatal disease. Bye v. Granite Co., 230 N.C. 334, 336, 53 S.E. 2d 274; Young v. Whitehall Co., 229 N.C. 360, 369, 49 S.E. 2d 797. Dust accumulates in and affects the lungs during exposure over long periods of time. Realizing this, the Legislature fixed by statute a rule for the guidance of the Industrial Commission in determining the period of last injurious exposure and placed liability upon the employer for whom employee was working during such period. It is important to both employer and employee that there be a definite rule for such determination. G.S. 97-57 provides that “. . . the employer in whose employment the employee was last injuriously exposed to the hazards of such disease, and the insurance carrier, if any, which was on the risk when the employee was bo last exposed under such employer’, shall be liable. For the purpose of this section when an employee has been exposed to the hazards of . . . silicosis for as much as thirty working days, or parts thereof, within seven consecutive calendar months, such exposure shall be deemed injurious but any less exposure shall not be deemed injurious.” This rule in its application to the instant case may be paraphrased as follows: The period of last injurious exposure is the last thirty days of employment while exposed to silica dust, provided employee works for the same employer as much as thirty days or .parts thereof in a period of seven months. An employee is capable of further injury so long as there is any sound tissue in the lung? to be scarred by the cutting particles of dust and reduced to a fibroid state; the law takes the *301breakdown where it occurs. Haynes v. Feldspar Producing Co., 222 N.C. 163, 170, 22 S.E. 2d 275. We must hold, as in the Haynes case, that employee was 'capable of further injury from silicosis up to and including 29 September 1951 because he still lived and breathed. G.S. 97-57 creates an irrebuttable presumption — a presumption of law. The last day of work was the date of disablement and the last ■thirty days of work was the period of last injurious exposure in the case at bar. The Commission may not arbitrarily select any 30 days of employment, other than the last 30 days, within the seven months period ;for convenience or protection of any of the parties, even if there is some evidence which may be construed to support such selection. Hartsell v. Thermoid Co., 249 N.C. 527, 107 S.E. 2d 115; Mayberry v. Marble Co., 243 N.C. 281, 90 S.E. 2d 511; Willingham v. Rock & Sand Co., 240 N.C. 281, 82 S.E. 2d 68; Stewart v. Duncan, 239 N.C. 640, 80 S.E. 2d 764; Bye v. Granite Co., supra; Haynes v. Feldspar Producing Co., supra.
In the case at baa’ the United States Fidelity & Guaranty Company was not on the risk during the period of last injurious exposure and the Commission properly dismissed it as party defendant. However, we wish to make it clear that there must be disablement as defined by G.S. 97-54 before ordinary compensation may be ¡awarded in silicosis eases. The time when disablement is deemed to have occurred depends upon the factual situation under consideration. Young v. Whitehall Co., supra; Singleton v. Mica Co., 235 N.C. 315, 69 S.E. 2d 707; Honeycutt v. Asbestos Co., 235 N.C. 471, 70 S.E. 2d 426. In the instant case G.S. 97-57 fixes the time of disablement and the period of last injurious exposure when applied to the facts. . ¡
Defendant insists that it is not liable for payment, in ¡any event, for the reason that employee waived 'Compensation in writing. • ■
It is true that employee on 10 August 1950 applied to ¡the Commission for leave to accept employment with Cole-Willard Stone Company of Raleigh 'and waived his rights to compensation for any aggravation of his then physical condition, “other than the right'to claim compensation for disability or death or batir as now provided” in G.S. 97-61, “in the event that continued exposure to silicosis incidental to such employment should result in disability or death, in which event compensation shall be payable for a period not to exceed one hundred weeks.” (Emphasis ours). The Commission permitted employee “to enter the employment as 'Stated, until 20 December 1950 'and nio further.” Pursuant thereto employee worked for Cole-Willard Stone Company until 19 October 1950. There was no such request, waiver 'and permission with respect to the employment by defendant.'
*302The essential elements of a waiver are: (1) the existence, at the time-of the alleged waiver, of a right, advantage or benefit; (2) the knowledge, actual or constructive, of the existence thereof; and (3) an intention to relinquish such right, advantage or benefit. 56 Am. Jui\, Waiver, sec. 12, p. 113. Applying these principles to the situation at hand, it is clear that defendant did not rely on and may not claim any benefit under the waiver signed by employee on 10 August 1950. At that time employee had no rights with respect to compensation from defendant and contemplated none so far as the record discloses. There is no indication that employee ever intended to relinquish any rights that he might have to compensation by and through defendant. Defendant was not a party to the waiver of 10 August 1950 and is not mentioned therein. It was limited by its .terms to employment by Cole-Willard Stone Company.
Furthermore, the signing of the waiver in order to obtain -employment by Oole-Willard Stone Company -did not reduce the compensation for the death of employee from ordinary compensation to that provided-by G.S. 97-61. G.S. 97-61 was rewritten as 97-61.1 to 97-61.7 by-Session Laws 1955, chapter 123, and iby Session Laws 1957, chapter 1217. .We consider it here as it existed prior to 1955. G.S. 97-61 makes provision for compensating and rehabilitating employees, not actually disabled, who would be benefited by being taken out of the dusty trade. It provides for temporary compensation until employment may be obtained in another occupation and payment for training purposes in -a new trade. It provides as follows: “If an employee has been so compensated . . . and he thereafter engages in any occupation which exposes him to the hazards of silicosis . . . without first having obtained the written approval of the Industrial Commission, neither he, his dependents, personal representatives nor any -other person shall be entitled to -any compensation for disablement -or death from silicosis . . . : Provided, however, that -an employer so affected, as an alternative to forced change of occupation, may, subject to the approval of the Industrial Commission, waive in writing his right to compensation for aggravation of -his condition that may result from his continuing in his hazardous occupation; but in the event of total disablement or death . . . -compensation shall nevertheless be payable, but in no case . . •. for a longer period than one hundred (100)- weeks.” (Emphasis ours).
Employee in the -case at bar did not at any time receive any compensation under G.S. 97-61 and therefore did not forfeit his right to compensation thereunder. Employee did not waive in writing his right to compensation when he was employed 'by defendant and'the Oom-*303mission did not approve his employment by defendant. Therefore, plaintiffs are entitled to ordinary compensation herein. Bye v. Granite Co., supra.
Defendant might have avoided liability, had it so desired, by insisting that employee be examined and a prompt report be made before it. received him into service. The refusal of employee to submit to such examination would have barred him from compensation. G.S. 97-60. Willingham v. Rock & Sand Co., supra; Haynes v. Feldspar Producing Co., supra.
G.S. 97-65 provides that “In case of disablement or death due primarily from silicosis . . . 'and complicated with tuberculosis of the lungs compensation shall be payable as hereinbefore provided, except that the rate of payment may be reduced one-sixth.” Whether the award should be so reduced rests in the discretion of the Industrial Commission. Stewart v. Duncan, supra.
There was competent evidence to support the findings of fact by the Industrial Commission and its conclusions of law are supported by -the findings of fact.
On appeal from the Industrial Commission, the Superior Court has only appellate jurisdiction to review an award of the Industrial Commission for errors of law. It may not find additional facts or make an award. Brice v. Salvage Co., 249 N.C. 74, 82, 105 S.E. 2d 439.
This case is remanded to the end that 'an order be made affirming the award of the Industrial Commission.
On defendant’s appeal — affirmed.
On carrier’s appeal — reversed.
Higgins, J., not sitting.